Date: Tue, 30 Nov 2021 15:35:18 -0600 From: Kyle Evans <kevans@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, "<dev-commits-src-all@freebsd.org>" <dev-commits-src-all@freebsd.org>, dev-commits-src-main@freebsd.org Subject: Re: git: 3d9d64aa1846 - main - kern_tc: unify timecounter to bintime delta conversion Message-ID: <CACNAnaFF49MVL%2B%2BRFOGbHH_dnFu7MvTHwc4zdbUN52=N=CT1bw@mail.gmail.com> In-Reply-To: <69d4804d-1d94-7757-5c93-0d062f9c31c0@FreeBSD.org> References: <202111301334.1AUDYJEU014078@gitrepo.freebsd.org> <CACNAnaGzuJuj_eZxA3y2vGrermmhH7BWkaa2OJv_WWtGXs98Zw@mail.gmail.com> <69d4804d-1d94-7757-5c93-0d062f9c31c0@FreeBSD.org>
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On Tue, Nov 30, 2021 at 11:08 AM Andriy Gapon <avg@freebsd.org> wrote: > > On 30/11/2021 18:14, Kyle Evans wrote: > > I wonder if this helps explain the behavior we saw when enabling TSC > > on VirtualBox guests. Threads doing small ~1 second or less sleeps > > would start to miss their wakeups, so we'd consistently see, e.g., > > shutdown issues after applying a high loading while we're waiting for > > bufdaemon threads. > > It very well may be the case. > The reason I arrived at this change is that we also sometimes saw the same > problem but on VMWware. That prompted me to add some diagnostic code to > sleepqueue to turn those missed wakeups into panics. > > As kib pointed out, mav recently made a change that would mask the problem as a > side effect: > https://cgit.FreeBSD.org/src/commit/?id=6df1359e5542f69179c142be1ea099d447e273d1 > But I wanted to fix the root cause anyway. > Ok, cool, thanks! I'll do some re-testing under VirtualBox and see if we can just revert this entirely: https://cgit.freebsd.org/src/commit/sys/x86/x86/tsc.c?id=8cc15b0dfc2f3299 Thanks, Kyle Evans
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