Date: Mon, 17 Dec 2007 22:37:25 -0500 From: Mark Fullmer <maf@eng.oar.net> To: David G Lawrence <dg@dglawrence.com> Cc: freebsd-net@freebsd.org, freebsd-stable@freebsd.org Subject: Re: Packet loss every 30.999 seconds Message-ID: <089C1524-B8E0-4C70-B69A-ECBE0C8DFC90@eng.oar.net> In-Reply-To: <20071217102433.GQ25053@tnn.dglawrence.com> References: <D50B5BA8-5A80-4370-8F20-6B3A531C2E9B@eng.oar.net> <20071217102433.GQ25053@tnn.dglawrence.com>
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Thanks. Have a kernel building now. It takes about a day of uptime
after reboot before I'll see the problem.
--
mark
On Dec 17, 2007, at 5:24 AM, David G Lawrence wrote:
>> While trying to diagnose a packet loss problem in a RELENG_6 snapshot
>> dated
>> November 8, 2007 it looks like I've stumbled across a broken
>> driver or
>> kernel routine which stops interrupt processing long enough to
>> severly
>> degrade network performance every 30.99 seconds.
>
> I noticed this as well some time ago. The problem has to do with
> the
> processing (syncing) of vnodes. When the total number of allocated
> vnodes
> in the system grows to tens of thousands, the ~31 second periodic sync
> process takes a long time to run. Try this patch and let people
> know if
> it helps your problem. It will periodically wait for one tick (1ms)
> every
> 500 vnodes of processing, which will allow other things to run.
>
> Index: ufs/ffs/ffs_vfsops.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/ufs/ffs/ffs_vfsops.c,v
> retrieving revision 1.290.2.16
> diff -c -r1.290.2.16 ffs_vfsops.c
> *** ufs/ffs/ffs_vfsops.c 9 Oct 2006 19:47:17 -0000 1.290.2.16
> --- ufs/ffs/ffs_vfsops.c 25 Apr 2007 01:58:15 -0000
> ***************
> *** 1109,1114 ****
> --- 1109,1115 ----
> int softdep_deps;
> int softdep_accdeps;
> struct bufobj *bo;
> + int flushed_count = 0;
>
> fs = ump->um_fs;
> if (fs->fs_fmod != 0 && fs->fs_ronly != 0) { /* XXX */
> ***************
> *** 1174,1179 ****
> --- 1175,1184 ----
> allerror = error;
> vput(vp);
> MNT_ILOCK(mp);
> + if (flushed_count++ > 500) {
> + flushed_count = 0;
> + msleep(&flushed_count, MNT_MTX(mp), PZERO, "syncw", 1);
> + }
> }
> MNT_IUNLOCK(mp);
> /*
>
> -DG
>
> David G. Lawrence
> President
> Download Technologies, Inc. - http://www.downloadtech.com - (866)
> 399 8500
> The FreeBSD Project - http://www.freebsd.org
> Pave the road of life with opportunities.
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