Date: Sat, 10 Jul 2004 15:30:35 +0800 From: Ariff Abdullah <skywizard@MyBSD.org.my> To: noackjr@alumni.rice.edu Cc: rwatson@freebsd.org Subject: Re: Native preemption is the culprit [was Re: today's CURRENT lockups] Message-ID: <20040710153035.1a525507.skywizard@MyBSD.org.my> In-Reply-To: <40EF96E7.3090608@alumni.rice.edu> References: <Pine.NEB.3.96L.1040709231313.19581G-100000@fledge.watson.org> <Pine.NEB.3.96L.1040710011206.19581H-100000@fledge.watson.org> <20040710150620.7595b207.skywizard@MyBSD.org.my> <40EF96E7.3090608@alumni.rice.edu>
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On Sat, 10 Jul 2004 02:12:39 -0500 Jon Noack <noackjr@alumni.rice.edu> wrote: > On 07/10/04 02:06, Ariff Abdullah wrote: > > On Sat, 10 Jul 2004 01:18:06 -0400 (EDT) > > Robert Watson <rwatson@freebsd.org> wrote: > >> FYI, UP+SCHED_ULE with PREEMPTION hung within three seconds of > >> starting the benchmark. Without PREEMPTION it seems to run fine. > >> > >> So it looks like either PREEMPTION has a problem, or it's > >> triggering an existing problem elsewhere. If it's only one > >problem,> it seems not to depend on either SMP/UP or the scheduler > >choice. If> it's multiple problems, who knows :-). As the MySQL > >test relies on > threading, we could be looking at an edge case > >involving threading > and scheduling/preemption-- the other reports > >I've seen mention > X11/KDE, which would also involve threading. On > >the other hand, it > could just be load. Tomorrow I'll load up a > >box with non-threaded > apps and see what happens. > > > > I'm suspecting bad combination between threaded apps and current > > native preemption, either the preemption itself, or threads. > > Running current kernel without any threaded apps turns up nothing > > suspicious. Once the threaded apps started, it's like sending the > > entire system to the death row. > > > > I'm reverting following files to pre-July 2 to achive solid > > stability: > > > > sys/sys/interrupt.h - v1.27 > > sys/kern/kern_intr.c - v1.110 > > sys/i386/i386/intr_machdep.c - v1.6 > > sys/kern/sched_ule.c - v1.109 > > Note that I haven't run across any issues after just reverting > sys/kern/sched_ule.c to rev. 1.113. The same workload > (X11/KDE/etc.) that crashes native preemption quite quickly has been > running solidly for over 14 hours now. > rev. 1.113 causing annoying latency issue (as stated in the commit log). Buildworld + xmms just ain't fun anymore. I think the main culprit is within ithread_schedule() itself, as it common to both ULE/4BSD. -- Ariff Abdullah MyBSD http://www.MyBSD.org.my (IPv6/IPv4) http://staff.MyBSD.org.my (IPv6/IPv4) http://tomoyo.MyBSD.org.my (IPv6/IPv4)
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