Date: Mon, 04 Mar 2019 22:07:54 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 236233] Python multiprocessing is 20x slower with 11.2 compared to 11.0 kernel Message-ID: <bug-236233-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D236233 Bug ID: 236233 Summary: Python multiprocessing is 20x slower with 11.2 compared to 11.0 kernel Product: Base System Version: 11.2-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: arichardson@FreeBSD.org After I updated our jenkins slaves from 11.0 to 11.2 running the LLVM regression test suite takes over 2 hours instead of 5-10 minutes. The testsuite is driven by llvm-lit (a python script) that makes heavy use = of python multiprocessing module. On 11.0 the test output prints status updates all the time whereas on 11.2 = it will print N (or N-1, N-2) status updates (with N being the number of paral= lel jobs) before a noticeable pause. In that pause it seems like the individual python processes start using 100% CPU. I tried updating one of the slaves to 12.0 but it is still just as slow. I also tried updating python27 to the latest 11.2 package (2.7.15) but that still runs fast. Therefore it seems to me like this could be a regression w= ith semaphores or umtx. I am also not sure if this is a regression in the kernel or libc/libthr. Downgrading to 11.0 fixes the issue. --=20 You are receiving this mail because: You are the assignee for the bug.=
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