Date: Tue, 8 Jan 2002 13:22:29 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: steve@Watt.COM (Steve Watt) Cc: stable@FreeBSD.ORG, re@FreeBSD.ORG Subject: Re: VXLOCK interlock avoided messages Message-ID: <200201082122.g08LMTp61466@apollo.backplane.com> References: <200201082110.g08LAqJ97852@wattres.Watt.COM>
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We changed this warning into a log() message, but perhaps we should
simply remove it entirely.
Basically there is no problem. This message is 'normal' now due to
us *finally* reclaiming vnodes when we've gone over the kern.maxvnodes
limit.
Normally vnodes are reclaimed only when their VM objects have no cached
pages left. This worked just fine until people starting putting 2G+
of ram into their machines. Once that started happening it was possible
to hit the kernel malloc pool limit for vnodes and/or inodes due to not
being able to free vnodes due to their VM objects still having cached
pages.
So now we reclaim vnodes proactively when the total number exceeds
kern.maxvnodes.
However, this has a side effect, for it means we are now reclaiming
vnodes which may still have dirty pages... dirty pages which now must
be flushed inside vgonel() while we hold VXLOCK. Flushing these pages
can often cause vget() to be called, which locks the vnodes and poof,
you get the warning.
It's a bogus warning. If the RE's agree I would like to simply remove
the associated log() calls.
-Matt
:Greetings!
:
:I recently upgraded to a fresher stable (4.5-PRE, 2002-Jan-3 20:43PST),
:and just saw (in my security report) the following very interesting
:looking errors:
:Jan 8 03:36:10 wattres /kernel: VXLOCK interlock avoided
:Jan 8 03:36:10 wattres /kernel: VXLOCK interlock avoided in vn_lock
:
:The box is usually pretty busy at that time of day running news expiry
:and the various odd cron jobs (daily, etc.). My news spool and libraries
:reside on different spindles, news articles on /news, news libraries
:on /old/local (filesystem list below).
:
:The previous update was 27 Oct in the evening PST, and I've never seen
:this message before.
:
:I see that it's a self-deadlock avoider in the code, but I don't
:know how to reproduce it (yet). I'll keep an eye on it and see if
:it occurs again.
:
:Mostly, this is a heads-up, and I'm wondering if anyone has seen this
:before and/or wants to gather more information.
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