From 2ead1ab91123d2af20dac4dfa551355dacfef00d Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 12 May 2017 10:09:50 +0000 Subject: [PATCH] Limit perf data buffer during profiling With high -j parallelism the autofdo tests can randomly fail. autofdo uses Linux perf to record profiling data. Linux perf uses a locked perf buffer. By default it has around 516k buffer per uid (/proc/sys/kernel/perf_event_mlock_kb). An individual perf record tries to grab the full 516k, which makes parallel perf record fail. This patch limits the perf buffer for individual perf record to 8k. With the default settings this allows a parallelism of the test cases of 16, which is hopefully good enough (if not would need to add some kind of semaphore, or ask the user to increase the limit as root) I also removed an unneeded -o perf.data option Thanks to Marcin to finally spotting the problem. Passes bootstrap and test on x86_64-linux. Ok for trunk? gcc/testsuite/: 2017-05-12 Andi Kleen PR testsuite/77684 * lib/target-supports.exp (profopt-perf-wrapper): Add -m8 option to increase parallelism. From-SVN: r247962 --- gcc/testsuite/ChangeLog | 6 ++++++ gcc/testsuite/lib/target-supports.exp | 9 ++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 13241be7df4..7b73b92759e 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2017-05-12 Andi Kleen + + PR testsuite/77684 + * lib/target-supports.exp (profopt-perf-wrapper): + Add -m8 option to increase parallelism. + 2017-05-12 Thomas Schwinge * c-c++-common/goacc/parallel-dims-1.c: New file. diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp index 83e7f2670e6..ded6383cc1f 100644 --- a/gcc/testsuite/lib/target-supports.exp +++ b/gcc/testsuite/lib/target-supports.exp @@ -522,9 +522,16 @@ proc check_effective_target_keeps_null_pointer_checks { } { # Return the autofdo profile wrapper +# Linux by default allows 516KB of perf event buffers +# in /proc/sys/kernel/perf_event_mlock_kb +# Each individual perf tries to grab it +# This causes problems with parallel test suite runs. Instead +# limit us to 8 pages (32K), which should be good enough +# for the small test programs. With the default settings +# this allows parallelism of 16 and higher of parallel gcc-auto-profile proc profopt-perf-wrapper { } { global srcdir - return "$srcdir/../config/i386/gcc-auto-profile -o perf.data " + return "$srcdir/../config/i386/gcc-auto-profile -o perf.data -m8 " } # Return true if profiling is supported on the target. -- 2.30.2