On May 18, 2017, at 1:35 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.
Not a big fan of warning. I'd rather smell the max, and divide by n, or limit them to 4 (or 16 or any fix constant) and pass appropriate arguments or anything else that just fixes it.
