KUDU-3557 Simple way to change maximum thread cache size of tcmalloc.

Now, Lock contention is too high in tcmalloc while the cluster in
under high throughput. Making the total thread cache size larger
could highly decrease the lock contention. Even though the max size
of one single thread cache could not be greater than 4096KB at the
first time, but it could request more from unclaimed cache space
or steal from other thread cache each time it's doing garbage
collection. For more details about tcmalloc, please check document:
https://gperftools.github.io/gperftools/tcmalloc.html

KUDU-3557 shows the difference on lock contention while setting
different sizes of max_total_thread_cache_bytes. Please check it
for details.

Change-Id: I3cb8c6ed6a8f24c63258ae65f8b841fe74b75308
Reviewed-on: http://gerrit.cloudera.org:8080/21076
Tested-by: Alexey Serbin <alexey@apache.org>
Reviewed-by: Alexey Serbin <alexey@apache.org>
2 files changed