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| <section id="memory-management"> |
| <span id="cpp-memory-management"></span><h1>Memory Management<a class="headerlink" href="#memory-management" title="Permalink to this heading">#</a></h1> |
| <div class="admonition seealso"> |
| <p class="admonition-title">See also</p> |
| <p><a class="reference internal" href="api/memory.html"><span class="doc">Memory management API reference</span></a></p> |
| </div> |
| <section id="buffers"> |
| <h2>Buffers<a class="headerlink" href="#buffers" title="Permalink to this heading">#</a></h2> |
| <p>To avoid passing around raw data pointers with varying and non-obvious |
| lifetime rules, Arrow provides a generic abstraction called <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6BufferE" title="arrow::Buffer"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::Buffer</span></code></a>. |
| A Buffer encapsulates a pointer and data size, and generally also ties its |
| lifetime to that of an underlying provider (in other words, a Buffer should |
| <em>always</em> point to valid memory till its destruction). Buffers are untyped: |
| they simply denote a physical memory area regardless of its intended meaning |
| or interpretation.</p> |
| <p>Buffers may be allocated by Arrow itself , or by third-party routines. |
| For example, it is possible to pass the data of a Python bytestring as a Arrow |
| buffer, keeping the Python object alive as necessary.</p> |
| <p>In addition, buffers come in various flavours: mutable or not, resizable or |
| not. Generally, you will hold a mutable buffer when building up a piece |
| of data, then it will be frozen as an immutable container such as an |
| <a class="reference internal" href="arrays.html"><span class="doc">array</span></a>.</p> |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>Some buffers may point to non-CPU memory, such as GPU-backed memory |
| provided by a CUDA context. If you’re writing a GPU-aware application, |
| you will need to be careful not to interpret a GPU memory pointer as |
| a CPU-reachable pointer, or vice-versa.</p> |
| </div> |
| <section id="accessing-buffer-memory"> |
| <h3>Accessing Buffer Memory<a class="headerlink" href="#accessing-buffer-memory" title="Permalink to this heading">#</a></h3> |
| <p>Buffers provide fast access to the underlying memory using the |
| <a class="reference internal" href="api/memory.html#_CPPv4NK5arrow6Buffer4sizeEv" title="arrow::Buffer::size"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">size()</span></code></a> and <a class="reference internal" href="api/memory.html#_CPPv4NK5arrow6Buffer4dataEv" title="arrow::Buffer::data"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">data()</span></code></a> accessors |
| (or <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6Buffer12mutable_dataEv" title="arrow::Buffer::mutable_data"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">mutable_data()</span></code></a> for writable access to a mutable |
| buffer).</p> |
| </section> |
| <section id="slicing"> |
| <h3>Slicing<a class="headerlink" href="#slicing" title="Permalink to this heading">#</a></h3> |
| <p>It is possible to make zero-copy slices of buffers, to obtain a buffer |
| referring to some contiguous subset of the underlying data. This is done |
| by calling the <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::SliceBuffer()</span></code> and <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::SliceMutableBuffer()</span></code> |
| functions.</p> |
| </section> |
| <section id="allocating-a-buffer"> |
| <h3>Allocating a Buffer<a class="headerlink" href="#allocating-a-buffer" title="Permalink to this heading">#</a></h3> |
| <p>You can allocate a buffer yourself by calling one of the |
| <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::AllocateBuffer()</span></code> or <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::AllocateResizableBuffer()</span></code> |
| overloads:</p> |
| <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="n">arrow</span><span class="o">::</span><span class="n">Result</span><span class="o"><</span><span class="n">std</span><span class="o">::</span><span class="n">unique_ptr</span><span class="o"><</span><span class="n">Buffer</span><span class="o">>></span><span class="w"> </span><span class="n">maybe_buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">AllocateBuffer</span><span class="p">(</span><span class="mi">4096</span><span class="p">);</span> |
| <span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">maybe_buffer</span><span class="p">.</span><span class="n">ok</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="c1">// ... handle allocation error</span> |
| <span class="p">}</span> |
| |
| <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">></span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">std</span><span class="o">::</span><span class="n">move</span><span class="p">(</span><span class="n">maybe_buffer</span><span class="p">);</span> |
| <span class="kt">uint8_t</span><span class="o">*</span><span class="w"> </span><span class="n">buffer_data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="o">-></span><span class="n">mutable_data</span><span class="p">();</span> |
| <span class="n">memcpy</span><span class="p">(</span><span class="n">buffer_data</span><span class="p">,</span><span class="w"> </span><span class="s">"hello world"</span><span class="p">,</span><span class="w"> </span><span class="mi">11</span><span class="p">);</span> |
| </pre></div> |
| </div> |
| <p>Allocating a buffer this way ensures it is 64-bytes aligned and padded |
| as recommended by the <a class="reference internal" href="../format/Layout.html"><span class="doc">Arrow memory specification</span></a>.</p> |
| </section> |
| <section id="building-a-buffer"> |
| <h3>Building a Buffer<a class="headerlink" href="#building-a-buffer" title="Permalink to this heading">#</a></h3> |
| <p>You can also allocate <em>and</em> build a Buffer incrementally, using the |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow13BufferBuilderE" title="arrow::BufferBuilder"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::BufferBuilder</span></code></a> API:</p> |
| <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="n">BufferBuilder</span><span class="w"> </span><span class="n">builder</span><span class="p">;</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Resize</span><span class="p">(</span><span class="mi">11</span><span class="p">);</span><span class="w"> </span><span class="c1">// reserve enough space for 11 bytes</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Append</span><span class="p">(</span><span class="s">"hello "</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">);</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Append</span><span class="p">(</span><span class="s">"world"</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">);</span> |
| |
| <span class="k">auto</span><span class="w"> </span><span class="n">maybe_buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="n">Finish</span><span class="p">();</span> |
| <span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">maybe_buffer</span><span class="p">.</span><span class="n">ok</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="c1">// ... handle buffer allocation error</span> |
| <span class="p">}</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">></span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">maybe_buffer</span><span class="p">;</span> |
| </pre></div> |
| </div> |
| <p>If a Buffer is meant to contain values of a given fixed-width type (for |
| example the 32-bit offsets of a List array), it can be more convenient to |
| use the template <a class="reference internal" href="api/memory.html#_CPPv4I00EN5arrow18TypedBufferBuilderE" title="arrow::TypedBufferBuilder"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::TypedBufferBuilder</span></code></a> API:</p> |
| <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="n">TypedBufferBuilder</span><span class="o"><</span><span class="kt">int32_t</span><span class="o">></span><span class="w"> </span><span class="n">builder</span><span class="p">;</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Reserve</span><span class="p">(</span><span class="mi">2</span><span class="p">);</span><span class="w"> </span><span class="c1">// reserve enough space for two int32_t values</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Append</span><span class="p">(</span><span class="mh">0x12345678</span><span class="p">);</span> |
| <span class="n">builder</span><span class="p">.</span><span class="n">Append</span><span class="p">(</span><span class="mh">-0x765643210</span><span class="p">);</span> |
| |
| <span class="k">auto</span><span class="w"> </span><span class="n">maybe_buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="n">Finish</span><span class="p">();</span> |
| <span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">maybe_buffer</span><span class="p">.</span><span class="n">ok</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="c1">// ... handle buffer allocation error</span> |
| <span class="p">}</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">></span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">maybe_buffer</span><span class="p">;</span> |
| </pre></div> |
| </div> |
| </section> |
| </section> |
| <section id="memory-pools"> |
| <span id="cpp-memory-pool"></span><h2>Memory Pools<a class="headerlink" href="#memory-pools" title="Permalink to this heading">#</a></h2> |
| <p>When allocating a Buffer using the Arrow C++ API, the buffer’s underlying |
| memory is allocated by a <a class="reference internal" href="api/memory.html#_CPPv4N5arrow10MemoryPoolE" title="arrow::MemoryPool"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::MemoryPool</span></code></a> instance. Usually this |
| will be the process-wide <em>default memory pool</em>, but many Arrow APIs allow |
| you to pass another MemoryPool instance for their internal allocations.</p> |
| <p>Memory pools are used for large long-lived data such as array buffers. |
| Other data, such as small C++ objects and temporary workspaces, usually |
| goes through the regular C++ allocators.</p> |
| <section id="default-memory-pool"> |
| <h3>Default Memory Pool<a class="headerlink" href="#default-memory-pool" title="Permalink to this heading">#</a></h3> |
| <p>The default memory pool depends on how Arrow C++ was compiled:</p> |
| <ul class="simple"> |
| <li><p>if enabled at compile time, a <a class="reference external" href="http://jemalloc.net/">jemalloc</a> heap;</p></li> |
| <li><p>otherwise, if enabled at compile time, a |
| <a class="reference external" href="https://github.com/microsoft/mimalloc">mimalloc</a> heap;</p></li> |
| <li><p>otherwise, the C library <code class="docutils literal notranslate"><span class="pre">malloc</span></code> heap.</p></li> |
| </ul> |
| </section> |
| <section id="overriding-the-default-memory-pool"> |
| <h3>Overriding the Default Memory Pool<a class="headerlink" href="#overriding-the-default-memory-pool" title="Permalink to this heading">#</a></h3> |
| <p>One can override the above selection algorithm by setting the |
| <span class="target" id="index-0"></span><a class="reference internal" href="env_vars.html#envvar-ARROW_DEFAULT_MEMORY_POOL"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">ARROW_DEFAULT_MEMORY_POOL</span></code></a> environment variable.</p> |
| </section> |
| <section id="stl-integration"> |
| <h3>STL Integration<a class="headerlink" href="#stl-integration" title="Permalink to this heading">#</a></h3> |
| <p>If you wish to use a Arrow memory pool to allocate the data of STL containers, |
| you can do so using the <a class="reference internal" href="api/memory.html#_CPPv4I0EN5arrow3stl9allocatorE" title="arrow::stl::allocator"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::stl::allocator</span></code></a> wrapper.</p> |
| <p>Conversely, you can also use a STL allocator to allocate Arrow memory, |
| using the <a class="reference internal" href="api/memory.html#_CPPv4I0EN5arrow3stl13STLMemoryPoolE" title="arrow::stl::STLMemoryPool"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::stl::STLMemoryPool</span></code></a> class. However, this may be less |
| performant, as STL allocators don’t provide a resizing operation.</p> |
| </section> |
| </section> |
| <section id="devices"> |
| <h2>Devices<a class="headerlink" href="#devices" title="Permalink to this heading">#</a></h2> |
| <p>Many Arrow applications only access host (CPU) memory. However, in some cases |
| it is desirable to handle on-device memory (such as on-board memory on a GPU) |
| as well as host memory.</p> |
| <p>Arrow represents the CPU and other devices using the |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6DeviceE" title="arrow::Device"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::Device</span></code></a> abstraction. The associated class <a class="reference internal" href="api/memory.html#_CPPv4N5arrow13MemoryManagerE" title="arrow::MemoryManager"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::MemoryManager</span></code></a> |
| specifies how to allocate on a given device. Each device has a default memory manager, but |
| additional instances may be constructed (for example, wrapping a custom |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow10MemoryPoolE" title="arrow::MemoryPool"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::MemoryPool</span></code></a> the CPU). |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow13MemoryManagerE" title="arrow::MemoryManager"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::MemoryManager</span></code></a> instances which specify how to allocate |
| memory on a given device (for example, using a particular |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow10MemoryPoolE" title="arrow::MemoryPool"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::MemoryPool</span></code></a> on the CPU).</p> |
| <section id="device-agnostic-programming"> |
| <h3>Device-Agnostic Programming<a class="headerlink" href="#device-agnostic-programming" title="Permalink to this heading">#</a></h3> |
| <p>If you receive a Buffer from third-party code, you can query whether it is |
| CPU-readable by calling its <a class="reference internal" href="api/memory.html#_CPPv4NK5arrow6Buffer6is_cpuEv" title="arrow::Buffer::is_cpu"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">is_cpu()</span></code></a> method.</p> |
| <p>You can also view the Buffer on a given device, in a generic way, by calling |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6Buffer4ViewENSt10shared_ptrI6BufferEERKNSt10shared_ptrI13MemoryManagerEE" title="arrow::Buffer::View"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::Buffer::View()</span></code></a> or <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6Buffer10ViewOrCopyENSt10shared_ptrI6BufferEERKNSt10shared_ptrI13MemoryManagerEE" title="arrow::Buffer::ViewOrCopy"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::Buffer::ViewOrCopy()</span></code></a>. This will |
| be a no-operation if the source and destination devices are identical. |
| Otherwise, a device-dependent mechanism will attempt to construct a memory |
| address for the destination device that gives access to the buffer contents. |
| Actual device-to-device transfer may happen lazily, when reading the buffer |
| contents.</p> |
| <p>Similarly, if you want to do I/O on a buffer without assuming a CPU-readable |
| buffer, you can call <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6Buffer9GetReaderENSt10shared_ptrI6BufferEE" title="arrow::Buffer::GetReader"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::Buffer::GetReader()</span></code></a> and |
| <a class="reference internal" href="api/memory.html#_CPPv4N5arrow6Buffer9GetWriterENSt10shared_ptrI6BufferEE" title="arrow::Buffer::GetWriter"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::Buffer::GetWriter()</span></code></a>.</p> |
| <p>For example, to get an on-CPU view or copy of an arbitrary buffer, you can |
| simply do:</p> |
| <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">></span><span class="w"> </span><span class="n">arbitrary_buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="p">;</span> |
| <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">></span><span class="w"> </span><span class="n">cpu_buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">Buffer</span><span class="o">::</span><span class="n">ViewOrCopy</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">arbitrary_buffer</span><span class="p">,</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">default_cpu_memory_manager</span><span class="p">());</span> |
| </pre></div> |
| </div> |
| </section> |
| </section> |
| <section id="memory-profiling"> |
| <h2>Memory Profiling<a class="headerlink" href="#memory-profiling" title="Permalink to this heading">#</a></h2> |
| <p>On Linux, detailed profiles of memory allocations can be generated using |
| <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">record</span></code>, without any need to modify the binaries. These profiles can |
| show the traceback in addition to allocation size. This does require debug |
| symbols, from either a debug build or a release with debug symbols build.</p> |
| <div class="admonition note"> |
| <p class="admonition-title">Note</p> |
| <p>If you are profiling Arrow’s tests on another platform, you can run the |
| following Docker container using Archery to access a Linux environment:</p> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>archery<span class="w"> </span>docker<span class="w"> </span>run<span class="w"> </span>ubuntu-cpp<span class="w"> </span>bash |
| <span class="c1"># Inside the Docker container...</span> |
| /arrow/ci/scripts/cpp_build.sh<span class="w"> </span>/arrow<span class="w"> </span>/build |
| <span class="nb">cd</span><span class="w"> </span>build/cpp/debug |
| ./arrow-array-test<span class="w"> </span><span class="c1"># Run a test</span> |
| apt-get<span class="w"> </span>update |
| apt-get<span class="w"> </span>install<span class="w"> </span>-y<span class="w"> </span>linux-tools-generic |
| <span class="nb">alias</span><span class="w"> </span><span class="nv">perf</span><span class="o">=</span>/usr/lib/linux-tools/<version-path>/perf |
| </pre></div> |
| </div> |
| </div> |
| <p>To track allocations, create probe points on each of the allocator methods used. |
| Collecting <code class="docutils literal notranslate"><span class="pre">$params</span></code> allows us to record the size of the allocations |
| requested, while collecting <code class="docutils literal notranslate"><span class="pre">$retval</span></code> allows us to record the address of |
| recorded allocations, so we can correlate them with the call to free/de-allocate.</p> |
| <div class="sd-tab-set docutils"> |
| <input checked="checked" id="sd-tab-item-0" name="sd-tab-set-0" type="radio"> |
| </input><label class="sd-tab-label" for="sd-tab-item-0"> |
| jemalloc</label><div class="sd-tab-content docutils"> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>je_arrow_mallocx<span class="w"> </span><span class="s1">'$params'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>je_arrow_mallocx%return<span class="w"> </span><span class="s1">'$retval'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>je_arrow_rallocx<span class="w"> </span><span class="s1">'$params'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>je_arrow_rallocx%return<span class="w"> </span><span class="s1">'$retval'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>je_arrow_dallocx<span class="w"> </span><span class="s1">'$params'</span> |
| <span class="nv">PROBE_ARGS</span><span class="o">=</span><span class="s2">"-e probe_libarrow:je_arrow_mallocx \</span> |
| <span class="s2"> -e probe_libarrow:je_arrow_mallocx__return \</span> |
| <span class="s2"> -e probe_libarrow:je_arrow_rallocx \</span> |
| <span class="s2"> -e probe_libarrow:je_arrow_rallocx__return \</span> |
| <span class="s2"> -e probe_libarrow:je_arrow_dallocx"</span> |
| </pre></div> |
| </div> |
| </div> |
| <input id="sd-tab-item-1" name="sd-tab-set-0" type="radio"> |
| </input><label class="sd-tab-label" for="sd-tab-item-1"> |
| mimalloc</label><div class="sd-tab-content docutils"> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>mi_malloc_aligned<span class="w"> </span><span class="s1">'$params'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>mi_malloc_aligned%return<span class="w"> </span><span class="s1">'$retval'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>mi_realloc_aligned<span class="w"> </span><span class="s1">'$params'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>mi_realloc_aligned%return<span class="w"> </span><span class="s1">'$retval'</span> |
| perf<span class="w"> </span>probe<span class="w"> </span>-x<span class="w"> </span>libarrow.so<span class="w"> </span>mi_free<span class="w"> </span><span class="s1">'$params'</span> |
| <span class="nv">PROBE_ARGS</span><span class="o">=</span><span class="s2">"-e probe_libarrow:mi_malloc_aligned \</span> |
| <span class="s2"> -e probe_libarrow:mi_malloc_aligned__return \</span> |
| <span class="s2"> -e probe_libarrow:mi_realloc_aligned \</span> |
| <span class="s2"> -e probe_libarrow:mi_realloc_aligned__return \</span> |
| <span class="s2"> -e probe_libarrow:mi_free"</span> |
| </pre></div> |
| </div> |
| </div> |
| </div> |
| <p>Once probes have been set, you can record calls with associated tracebacks using |
| <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">record</span></code>. In this example, we are running the StructArray unit tests in |
| Arrow:</p> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>perf<span class="w"> </span>record<span class="w"> </span>-g<span class="w"> </span>--call-graph<span class="w"> </span>dwarf<span class="w"> </span><span class="se">\</span> |
| <span class="w"> </span><span class="nv">$PROBE_ARGS</span><span class="w"> </span><span class="se">\</span> |
| <span class="w"> </span>./arrow-array-test<span class="w"> </span>--gtest_filter<span class="o">=</span>StructArray* |
| </pre></div> |
| </div> |
| <p>If you want to profile a running process, you can run <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">record</span> <span class="pre">-p</span> <span class="pre"><PID></span></code> |
| and it will record until you interrupt with CTRL+C. Alternatively, you can do |
| <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">record</span> <span class="pre">-P</span> <span class="pre"><PID></span> <span class="pre">sleep</span> <span class="pre">10</span></code> to record for 10 seconds.</p> |
| <p>The resulting data can be processed with standard tools to work with perf or |
| <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">script</span></code> can be used to pipe a text format of the data to custom scripts. |
| The following script parses <code class="docutils literal notranslate"><span class="pre">perf</span> <span class="pre">script</span></code> output and prints the output in |
| new lines delimited JSON for easier processing.</p> |
| <div class="literal-block-wrapper docutils container" id="id1"> |
| <div class="code-block-caption"><span class="caption-text">process_perf_events.py</span><a class="headerlink" href="#id1" title="Permalink to this code">#</a></div> |
| <div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span> |
| <span class="kn">import</span> <span class="nn">re</span> |
| <span class="kn">import</span> <span class="nn">json</span> |
| |
| <span class="c1"># Example non-traceback line</span> |
| <span class="c1"># arrow-array-tes 14344 [003] 7501.073802: probe_libarrow:je_arrow_mallocx: (7fbcd20bb640) size=0x80 flags=6</span> |
| |
| <span class="n">current</span> <span class="o">=</span> <span class="p">{}</span> |
| <span class="n">current_traceback</span> <span class="o">=</span> <span class="s1">''</span> |
| |
| <span class="k">def</span> <span class="nf">new_row</span><span class="p">():</span> |
| <span class="k">global</span> <span class="n">current_traceback</span> |
| <span class="n">current</span><span class="p">[</span><span class="s1">'traceback'</span><span class="p">]</span> <span class="o">=</span> <span class="n">current_traceback</span> |
| <span class="nb">print</span><span class="p">(</span><span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">current</span><span class="p">))</span> |
| <span class="n">current_traceback</span> <span class="o">=</span> <span class="s1">''</span> |
| |
| <span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="n">sys</span><span class="o">.</span><span class="n">stdin</span><span class="p">:</span> |
| <span class="k">if</span> <span class="n">line</span> <span class="o">==</span> <span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">:</span> |
| <span class="k">continue</span> |
| <span class="k">elif</span> <span class="n">line</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="s1">'</span><span class="se">\t</span><span class="s1">'</span><span class="p">:</span> |
| <span class="c1"># traceback line</span> |
| <span class="n">current_traceback</span> <span class="o">+=</span> <span class="n">line</span><span class="o">.</span><span class="n">strip</span><span class="p">(</span><span class="s2">"</span><span class="se">\t</span><span class="s2">"</span><span class="p">)</span> |
| <span class="k">else</span><span class="p">:</span> |
| <span class="n">line</span> <span class="o">=</span> <span class="n">line</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> |
| <span class="k">if</span> <span class="ow">not</span> <span class="nb">len</span><span class="p">(</span><span class="n">current</span><span class="p">)</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span> |
| <span class="n">new_row</span><span class="p">()</span> |
| <span class="n">parts</span> <span class="o">=</span> <span class="n">re</span><span class="o">.</span><span class="n">sub</span><span class="p">(</span><span class="s1">' +'</span><span class="p">,</span> <span class="s1">' '</span><span class="p">,</span> <span class="n">line</span><span class="p">)</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">' '</span><span class="p">)</span> |
| |
| <span class="n">parts</span><span class="o">.</span><span class="n">reverse</span><span class="p">()</span> |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> <span class="c1"># file</span> |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> <span class="c1"># "14344"</span> |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> <span class="c1"># "[003]"</span> |
| |
| <span class="n">current</span><span class="p">[</span><span class="s1">'time'</span><span class="p">]</span> <span class="o">=</span> <span class="nb">float</span><span class="p">(</span><span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="s2">":"</span><span class="p">))</span> |
| <span class="n">current</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">=</span> <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="s2">":"</span><span class="p">)</span> |
| |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> <span class="c1"># (7fbcd20bddf0)</span> |
| <span class="k">if</span> <span class="n">parts</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"<-"</span><span class="p">:</span> |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> |
| <span class="n">parts</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span> |
| |
| <span class="n">params</span> <span class="o">=</span> <span class="p">{}</span> |
| |
| <span class="k">for</span> <span class="n">pair</span> <span class="ow">in</span> <span class="n">parts</span><span class="p">:</span> |
| <span class="n">key</span><span class="p">,</span> <span class="n">value</span> <span class="o">=</span> <span class="n">pair</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s2">"="</span><span class="p">)</span> |
| <span class="n">params</span><span class="p">[</span><span class="n">key</span><span class="p">]</span> <span class="o">=</span> <span class="n">value</span> |
| |
| <span class="n">current</span><span class="p">[</span><span class="s1">'params'</span><span class="p">]</span> <span class="o">=</span> <span class="n">params</span> |
| </pre></div> |
| </div> |
| </div> |
| <p>Here’s an example invocation of that script, with a preview of output data:</p> |
| <div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>perf<span class="w"> </span>script<span class="w"> </span><span class="p">|</span><span class="w"> </span>python3<span class="w"> </span>/arrow/process_perf_events.py<span class="w"> </span>><span class="w"> </span>processed_events.jsonl |
| <span class="gp">$ </span>head<span class="w"> </span>processed_events.jsonl<span class="w"> </span><span class="p">|</span><span class="w"> </span>cut<span class="w"> </span>-c<span class="w"> </span>-120 |
| <span class="go">{"time": 14814.954378, "event": "probe_libarrow:je_arrow_mallocx", "params": {"flags": "6", "size": "0x80"}, "traceback"</span> |
| <span class="go">{"time": 14814.95443, "event": "probe_libarrow:je_arrow_mallocx__return", "params": {"arg1": "0x7f4a97e09000"}, "traceba</span> |
| <span class="go">{"time": 14814.95448, "event": "probe_libarrow:je_arrow_mallocx", "params": {"flags": "6", "size": "0x40"}, "traceback":</span> |
| <span class="go">{"time": 14814.954486, "event": "probe_libarrow:je_arrow_mallocx__return", "params": {"arg1": "0x7f4a97e0a000"}, "traceb</span> |
| <span class="go">{"time": 14814.954502, "event": "probe_libarrow:je_arrow_rallocx", "params": {"flags": "6", "size": "0x40", "ptr": "0x7f</span> |
| <span class="go">{"time": 14814.954507, "event": "probe_libarrow:je_arrow_rallocx__return", "params": {"arg1": "0x7f4a97e0a040"}, "traceb</span> |
| <span class="go">{"time": 14814.954796, "event": "probe_libarrow:je_arrow_mallocx", "params": {"flags": "6", "size": "0x40"}, "traceback"</span> |
| <span class="go">{"time": 14814.954805, "event": "probe_libarrow:je_arrow_mallocx__return", "params": {"arg1": "0x7f4a97e0a080"}, "traceb</span> |
| <span class="go">{"time": 14814.954817, "event": "probe_libarrow:je_arrow_mallocx", "params": {"flags": "6", "size": "0x40"}, "traceback"</span> |
| <span class="go">{"time": 14814.95482, "event": "probe_libarrow:je_arrow_mallocx__return", "params": {"arg1": "0x7f4a97e0a0c0"}, "traceba</span> |
| </pre></div> |
| </div> |
| <p>From there one can answer a number of questions. For example, the following |
| script will find which allocations were never freed, and print the associated |
| tracebacks along with the count of dangling allocations:</p> |
| <div class="literal-block-wrapper docutils container" id="id2"> |
| <div class="code-block-caption"><span class="caption-text">count_tracebacks.py</span><a class="headerlink" href="#id2" title="Permalink to this code">#</a></div> |
| <div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="sd">'''Find tracebacks of allocations with no corresponding free'''</span> |
| <span class="kn">import</span> <span class="nn">sys</span> |
| <span class="kn">import</span> <span class="nn">json</span> |
| <span class="kn">from</span> <span class="nn">collections</span> <span class="kn">import</span> <span class="n">defaultdict</span> |
| |
| <span class="n">allocated</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">()</span> |
| |
| <span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="n">sys</span><span class="o">.</span><span class="n">stdin</span><span class="p">:</span> |
| <span class="n">line</span> <span class="o">=</span> <span class="n">line</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> |
| <span class="n">data</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">line</span><span class="p">)</span> |
| |
| <span class="k">if</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:je_arrow_mallocx__return"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'arg1'</span><span class="p">]</span> |
| <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'traceback'</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:je_arrow_rallocx"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'ptr'</span><span class="p">]</span> |
| <span class="k">del</span> <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:je_arrow_rallocx__return"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'arg1'</span><span class="p">]</span> |
| <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'traceback'</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:je_arrow_dallocx"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'ptr'</span><span class="p">]</span> |
| <span class="k">if</span> <span class="n">address</span> <span class="ow">in</span> <span class="n">allocated</span><span class="p">:</span> |
| <span class="k">del</span> <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:mi_malloc_aligned__return"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'arg1'</span><span class="p">]</span> |
| <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'traceback'</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:mi_realloc_aligned"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'p'</span><span class="p">]</span> |
| <span class="k">del</span> <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:mi_realloc_aligned__return"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'arg1'</span><span class="p">]</span> |
| <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'traceback'</span><span class="p">]</span> |
| <span class="k">elif</span> <span class="n">data</span><span class="p">[</span><span class="s1">'event'</span><span class="p">]</span> <span class="o">==</span> <span class="s2">"probe_libarrow:mi_free"</span><span class="p">:</span> |
| <span class="n">address</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="s1">'params'</span><span class="p">][</span><span class="s1">'p'</span><span class="p">]</span> |
| <span class="k">if</span> <span class="n">address</span> <span class="ow">in</span> <span class="n">allocated</span><span class="p">:</span> |
| <span class="k">del</span> <span class="n">allocated</span><span class="p">[</span><span class="n">address</span><span class="p">]</span> |
| |
| <span class="n">traceback_counts</span> <span class="o">=</span> <span class="n">defaultdict</span><span class="p">(</span><span class="nb">int</span><span class="p">)</span> |
| |
| <span class="k">for</span> <span class="n">traceback</span> <span class="ow">in</span> <span class="n">allocated</span><span class="o">.</span><span class="n">values</span><span class="p">():</span> |
| <span class="n">traceback_counts</span><span class="p">[</span><span class="n">traceback</span><span class="p">]</span> <span class="o">+=</span> <span class="mi">1</span> |
| |
| <span class="k">for</span> <span class="n">traceback</span><span class="p">,</span> <span class="n">count</span> <span class="ow">in</span> <span class="nb">sorted</span><span class="p">(</span><span class="n">traceback_counts</span><span class="o">.</span><span class="n">items</span><span class="p">(),</span> <span class="n">key</span><span class="o">=</span><span class="k">lambda</span> <span class="n">x</span><span class="p">:</span> <span class="o">-</span><span class="n">x</span><span class="p">[</span><span class="mi">1</span><span class="p">]):</span> |
| <span class="nb">print</span><span class="p">(</span><span class="s2">"Num of dangling allocations:"</span><span class="p">,</span> <span class="n">count</span><span class="p">)</span> |
| <span class="nb">print</span><span class="p">(</span><span class="n">traceback</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| </div> |
| <p>The script can be invoked like so:</p> |
| <div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>cat<span class="w"> </span>processed_events.jsonl<span class="w"> </span><span class="p">|</span><span class="w"> </span>python3<span class="w"> </span>/arrow/count_tracebacks.py |
| <span class="go">Num of dangling allocations: 1</span> |
| <span class="go"> 7fc945e5cfd2 arrow::(anonymous namespace)::JemallocAllocator::ReallocateAligned+0x13b (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 7fc945e5fe4f arrow::BaseMemoryPoolImpl<arrow::(anonymous namespace)::JemallocAllocator>::Reallocate+0x93 (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 7fc945e618f7 arrow::PoolBuffer::Resize+0xed (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 55a38b163859 arrow::BufferBuilder::Resize+0x12d (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 55a38b163bbe arrow::BufferBuilder::Finish+0x48 (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 55a38b163e3a arrow::BufferBuilder::Finish+0x50 (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 55a38b163f90 arrow::BufferBuilder::FinishWithLength+0x4e (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 55a38b2c8fa7 arrow::TypedBufferBuilder<int, void>::FinishWithLength+0x4f (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 55a38b2bcce7 arrow::NumericBuilder<arrow::Int32Type>::FinishInternal+0x107 (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 7fc945c065ae arrow::ArrayBuilder::Finish+0x5a (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 7fc94736ed41 arrow::ipc::internal::json::(anonymous namespace)::Converter::Finish+0x123 (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 7fc94737426e arrow::ipc::internal::json::ArrayFromJSON+0x299 (/build/cpp/debug/libarrow.so.700.0.0)</span> |
| <span class="go"> 7fc948e98858 arrow::ArrayFromJSON+0x64 (/build/cpp/debug/libarrow_testing.so.700.0.0)</span> |
| <span class="go"> 55a38b6773f3 arrow::StructArray_FlattenOfSlice_Test::TestBody+0x79 (/build/cpp/debug/arrow-array-test)</span> |
| <span class="go"> 7fc944689633 testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>+0x68 (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc94468132a testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>+0x5d (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc9446555eb testing::Test::Run+0xf1 (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc94465602d testing::TestInfo::Run+0x13f (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc944656947 testing::TestSuite::Run+0x14b (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc9446663f5 testing::internal::UnitTestImpl::RunAllTests+0x433 (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc94468ab61 testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>+0x68 (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc944682568 testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>+0x5d (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc944664b0c testing::UnitTest::Run+0xcc (/build/cpp/googletest_ep-prefix/lib/libgtestd.so.1.11.0)</span> |
| <span class="go"> 7fc9446d0299 RUN_ALL_TESTS+0x14 (/build/cpp/googletest_ep-prefix/lib/libgtest_maind.so.1.11.0)</span> |
| <span class="go"> 7fc9446d021b main+0x42 (/build/cpp/googletest_ep-prefix/lib/libgtest_maind.so.1.11.0)</span> |
| <span class="go"> 7fc9441e70b2 __libc_start_main+0xf2 (/usr/lib/x86_64-linux-gnu/libc-2.31.so)</span> |
| <span class="go"> 55a38b10a50d _start+0x2d (/build/cpp/debug/arrow-array-test)</span> |
| </pre></div> |
| </div> |
| </section> |
| </section> |
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| </article> |
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