Date: Sat, 22 Dec 2007 01:28:31 -0500 From: Mark Fullmer <maf@splintered.net> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-net@freebsd.org, freebsd-stable@freebsd.org Subject: Re: Packet loss every 30.999 seconds Message-ID: <3647BB78-BA10-432B-A52B-04E402E155CC@splintered.net> In-Reply-To: <20071222053648.GQ57756@deviant.kiev.zoral.com.ua> References: <D50B5BA8-5A80-4370-8F20-6B3A531C2E9B@eng.oar.net> <20071217102433.GQ25053@tnn.dglawrence.com> <CD187AD1-8712-418F-9F49-FA3407BA1AC7@eng.oar.net> <20071220011626.U928@besplex.bde.org> <814DB7A9-E64F-4BCA-A502-AB5A6E0297D3@eng.oar.net> <20071219171331.GH25053@tnn.dglawrence.com> <20071221200810.GY16982@elvis.mu.org> <20071221234347.GS25053@tnn.dglawrence.com> <6D374B4C-0D98-4916-A762-7A85912B3058@splintered.net> <20071222053648.GQ57756@deviant.kiev.zoral.com.ua>
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On Dec 22, 2007, at 12:36 AM, Kostik Belousov wrote:
> On Fri, Dec 21, 2007 at 10:30:51PM -0500, Mark Fullmer wrote:
>> The uio_yield() idea did not work. Still have the same 31 second
>> interval packet loss.
> What patch you have used ?
This is hand applied from the diff you sent December 19, 2007 1:24:48
PM EST
sr1400-ar0.eng:/usr/src/sys/ufs/ffs# diff -c ffs_vfsops.c
ffs_vfsops.c.orig
*** ffs_vfsops.c Fri Dec 21 21:08:39 2007
--- ffs_vfsops.c.orig Sat Dec 22 00:51:22 2007
***************
*** 1107,1113 ****
struct ufsmount *ump = VFSTOUFS(mp);
struct fs *fs;
int error, count, wait, lockreq, allerror = 0;
- int yield_count;
int suspend;
int suspended;
int secondary_writes;
--- 1107,1112 ----
***************
*** 1148,1154 ****
softdep_get_depcounts(mp, &softdep_deps, &softdep_accdeps);
MNT_ILOCK(mp);
- yield_count = 0;
MNT_VNODE_FOREACH(vp, mp, mvp) {
/*
* Depend on the mntvnode_slock to keep things
stable enough
--- 1147,1152 ----
***************
*** 1166,1177 ****
(IN_ACCESS | IN_CHANGE | IN_MODIFIED |
IN_UPDATE)) == 0 &&
vp->v_bufobj.bo_dirty.bv_cnt == 0)) {
VI_UNLOCK(vp);
- if (yield_count++ == 100) {
- MNT_IUNLOCK(mp);
- yield_count = 0;
- uio_yield();
- goto relock_mp;
- }
continue;
}
MNT_IUNLOCK(mp);
--- 1164,1169 ----
***************
*** 1186,1192 ****
if ((error = ffs_syncvnode(vp, waitfor)) != 0)
allerror = error;
vput(vp);
- relock_mp:
MNT_ILOCK(mp);
}
MNT_IUNLOCK(mp);
--- 1178,1183 ----
>
> Lets check whether the syncer is the culprit for you.
> Please, change the value of the syncdelay at the sys/kern/vfs_subr.c
> around the line 238 from 30 to some other value, e.g., 45. After that,
> check the interval of the effect you have observed.
Changed it to 13. Not sure if SYNCER_MAXDELAY also needed to be
increased if syncdelay was increased.
static int syncdelay = 13; /* max time to delay syncing
data */
Test:
; use vnodes
% find / -type f -print > /dev/null
; verify
% sysctl vfs.numvnodes
vfs.numvnodes: 32128
; run packet loss test
now have periodic loss every 13994633us (13.99 seconds).
; reduce # of vnodes with sysctl kern.maxvnodes=1000
test now runs clean.
>
> It would be interesting to check whether completely disabling the
> syncer
> eliminates the packet loss, but such system have to be operated with
> extreme caution.
>
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