Merge pull request #40 from grossman/scheduler_usage_diff_divide_by_zero
Avoid divide by zero in scheduler_usage/1 on lightly loaded systems.
diff --git a/src/recon_lib.erl b/src/recon_lib.erl
index dc72256..5a49cf3 100644
--- a/src/recon_lib.erl
+++ b/src/recon_lib.erl
@@ -218,7 +218,9 @@
TotalTime :: non_neg_integer().
scheduler_usage_diff(First, Last) ->
lists:map(
- fun({{I, A0, T0}, {I, A1, T1}}) -> {I, (A1 - A0)/(T1 - T0)} end,
+ fun ({{I, _A0, T}, {I, _A1, T}}) -> {I, 0.0}; % Avoid divide by zero
+ ({{I, A0, T0}, {I, A1, T1}}) -> {I, (A1 - A0)/(T1 - T0)}
+ end,
lists:zip(lists:sort(First), lists:sort(Last))
).
diff --git a/test/recon_lib_SUITE.erl b/test/recon_lib_SUITE.erl
new file mode 100644
index 0000000..4a69df3
--- /dev/null
+++ b/test/recon_lib_SUITE.erl
@@ -0,0 +1,17 @@
+-module(recon_lib_SUITE).
+-include_lib("common_test/include/ct.hrl").
+-compile(export_all).
+
+all() -> [scheduler_usage_diff].
+
+scheduler_usage_diff(_Config) ->
+ {Active0, Total0} = {1000, 2000},
+ SchedStat0 = {1, Active0, Total0},
+ % No active or total time has elapsed. Make sure we don't divide by zero.
+ [{1, 0.0}] = recon_lib:scheduler_usage_diff([SchedStat0], [SchedStat0]),
+ % Total time has elapsed, but no active time. Make sure we get 0 usage back.
+ SchedStat1 = {1, Active0, Total0 * 2},
+ [{1, 0.0}] = recon_lib:scheduler_usage_diff([SchedStat0], [SchedStat1]),
+ % Check for 100% usage
+ SchedStat2 = {1, Active0 + 1000, Total0 + 1000},
+ [{1, 1.0}] = recon_lib:scheduler_usage_diff([SchedStat0], [SchedStat2]).
