On Thu, May 18, 2017 at 10:35 AM, Aldy Hernandez <al...@redhat.com> wrote: > Andi Kleen <a...@firstfloor.org> writes: > >> From: Andi Kleen <a...@linux.intel.com> >> >> 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 > > So for -jN > 16 it would silently fail again? > > I think we should warn when the -jN is sufficiently large such that > tests will randomly fail, and perhaps suggest workarounds with > ulimit/etc.
given that make check parallelism is somewhat "explicit" can't we simply arrange for the chunks to never get more than, say, 4 tree-prof.exp testcases run at the same time? Richard. > Aldy
