Date: Thu, 5 Feb 2015 01:19:53 -0800 From: Alfred Perlstein <bright@mu.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Current <freebsd-current@freebsd.org>, Dimitry Andric <dim@FreeBSD.org>, "Lundberg, Johannes" <johannes@brilliantservice.co.jp>, Allan Jude <allanjude@freebsd.org> Subject: Re: Weird behavior writing to SSD on 2013 MacBook Message-ID: <D0C3024E-FEE9-486F-AEAE-F66720A86FC3@mu.org> In-Reply-To: <20150205090324.GI42409@kib.kiev.ua> References: <CAASDrV=d=7aGdsDzDxRS2aXW%2BtWijVmNWrCNSYLWrWWvgwYx6Q@mail.gmail.com> <54D2C3DA.4060205@freebsd.org> <CAASDrV=9zrG8mH0Cn770yJLG6cBxuFjBQthhcHB_q4e7Afthww@mail.gmail.com> <CAASDrVnY8RQV2C=k=_v=23VD%2BQcXYegm1SLQPXDULwfQQ1xsDA@mail.gmail.com> <54D319EA.5020709@freebsd.org> <CAASDrVmcOzQiNMhi5dukd4PEyGXV4_T71jh3E3DfaWjKWWWM6g@mail.gmail.com> <AF0781EF-50BD-4CAB-8FEC-6334EED6DACF@FreeBSD.org> <20150205083035.GF42409@kib.kiev.ua> <54D32DC3.6020409@mu.org> <20150205090324.GI42409@kib.kiev.ua>
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It's possible original intent of that construct was just a pause/throttle if it used to be an if(). Makes sense although should investigate further. Sent from my iPhone > On Feb 5, 2015, at 1:03 AM, Konstantin Belousov <kostikbel@gmail.com> wrote: > >> On Thu, Feb 05, 2015 at 12:45:55AM -0800, Alfred Perlstein wrote: >> >> >>> On 2/5/15 12:30 AM, Konstantin Belousov wrote: >>>> On Thu, Feb 05, 2015 at 08:56:59AM +0100, Dimitry Andric wrote: >>>> If you let bsdtar continue, and press control-T a few times, does the >>>> user time (u) increase at all? Does it ever go any further, if you let >>>> it run for a very long time? >>>> >>>> I believe a problem may have been introduced by r277922, leading to >>>> filesystem hangs in some scenarios. It looks like this commit is also >>>> in dumbbell's github fork: >>>> >>>> https://github.com/dumbbell/freebsd/commit/83723416a6bb8695d60c6573722a81086899f521 >>> >>> Would be nice if you mailed me with your findings. >>> >>> Please try this. >>> >>> diff --git a/sys/ufs/ffs/ffs_softdep.c b/sys/ufs/ffs/ffs_softdep.c >>> index 79783c8..700854e 100644 >>> --- a/sys/ufs/ffs/ffs_softdep.c >>> +++ b/sys/ufs/ffs/ffs_softdep.c >>> @@ -1393,7 +1393,7 @@ softdep_flush(addr) >>> VFSTOUFS(mp)->softdep_jblocks->jb_suspended)) >>> kthread_suspend_check(); >>> ACQUIRE_LOCK(ump); >>> - while ((ump->softdep_flags & (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) >>> + if ((ump->softdep_flags & (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) >>> msleep(&ump->softdep_flushtd, LOCK_PTR(ump), PVM, >>> "sdflush", hz / 2); >>> ump->softdep_flags &= ~FLUSH_CLEANUP; >>> @@ -1423,10 +1423,9 @@ worklist_speedup(mp) >>> >>> ump = VFSTOUFS(mp); >>> LOCK_OWNED(ump); >>> - if ((ump->softdep_flags & (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) { >>> + if ((ump->softdep_flags & (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) >>> ump->softdep_flags |= FLUSH_CLEANUP; >>> - wakeup(&ump->softdep_flushtd); >>> - } >>> + wakeup(&ump->softdep_flushtd); >>> } >>> >>> static int >>> @@ -1471,11 +1470,10 @@ softdep_speedup(ump) >>> TAILQ_INSERT_TAIL(&softdepmounts, sdp, sd_next); >>> FREE_GBLLOCK(&lk); >>> if ((altump->softdep_flags & >>> - (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) { >>> + (FLUSH_CLEANUP | FLUSH_EXIT)) == 0) >>> altump->softdep_flags |= FLUSH_CLEANUP; >>> - altump->um_softdep->sd_cleanups++; >>> - wakeup(&altump->softdep_flushtd); >>> - } >>> + altump->um_softdep->sd_cleanups++; >>> + wakeup(&altump->softdep_flushtd); >>> FREE_LOCK(altump); >>> } >>> } >>> _______________________________________________ >> >> Why the conversion of while() to if()? >> >> >> The reason for a while() when doing msleep/wakeup is typically to >> prevent superfluous wakeups from signalling early. > > if()->while() was one of the changes in r277922, and I suspect that it > is the cause of the issue. I.e. my thought right now is that > softdep_process_worklist() does not keep up with the requests. > > If this is true, then real fix is somewhere else, but restoring > pre-r277922 behaviour should get rid of immediate pain. >help
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