Date: Wed, 4 Sep 2013 09:58:48 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-stable@freebsd.org Cc: J David <j.david.lists@gmail.com>, Eric van Gyzen <eric@vangyzen.net>, avg@freebsd.org, dave@mischler.com Subject: Re: unexpected idprio 31 behavior on 9.2-BETA2 and 9.2-RC1 Message-ID: <201309040958.48377.jhb@freebsd.org> In-Reply-To: <5203AE08.30504@vangyzen.net> References: <1375737316.96778.10.camel@firkin.mischler.com> <5203A90D.6020008@vangyzen.net> <5203AE08.30504@vangyzen.net>
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On Thursday, August 08, 2013 10:41:12 am Eric van Gyzen wrote: > On 08/08/2013 09:19, Eric van Gyzen wrote: > > On 08/06/2013 14:23, J David wrote: > >> On Tue, Aug 6, 2013 at 1:59 PM, Eric van Gyzen <eric@vangyzen.net> wrote: > >>>> on an otherwise idle amd64 system with 4 CPUs. The first command in the > >>>> build.log file: > >>>> > >>>> rm -rf /usr/obj/home/freebsd/tmp > >>>> > >>>> took over three minutes. It should have taken about three /seconds/. > >>>> > >>>> "uptime" reported a load average of around 1.00. > >>>> "top" showed no threads (user or kernel) using CPU. > >>>> "iostat" showed an average of less than 20 tps on ada0. > >>>> "rm" was usually in the RUN state. > >> We are looking at something similar. Would you be able to try to > >> reproduce it using a kernel with: > >> > >> nooptions SCHED_ULE > >> options SCHED_4BSD > >> > >> to see if it makes a difference? It seems to, but the problem is > >> inconsistent enough that I can't be sure. > > The 4BSD scheduler does //not// exhibit this problem. I tested with the > > latest releng/9.2 (r254054) and an otherwise GENERIC config. > > To be thorough, I built a GENERIC kernel at the same rev, and it still > exhibits the problem. Please try this change: Index: sched_ule.c =================================================================== --- sched_ule.c (revision 255020) +++ sched_ule.c (working copy) @@ -243,7 +243,7 @@ struct tdq { int tdq_transferable; /* Transferable thread count. */ short tdq_switchcnt; /* Switches this tick. */ short tdq_oldswitchcnt; /* Switches last tick. */ - u_char tdq_lowpri; /* Lowest priority thread. */ + u_short tdq_lowpri; /* Lowest priority thread. */ u_char tdq_ipipending; /* IPI pending. */ u_char tdq_idx; /* Current insert index. */ u_char tdq_ridx; /* Current removal index. */ @@ -2323,7 +2323,7 @@ sched_choose(void) tdq->tdq_lowpri = td->td_priority; return (td); } - tdq->tdq_lowpri = PRI_MAX_IDLE; + tdq->tdq_lowpri = PRI_MAX_IDLE + 1; return (PCPU_GET(idlethread)); } -- John Baldwin
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