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Date:      Sat, 19 Jan 2008 17:51:51 +0000
From:      Thomas Hurst <tom.hurst@clara.net>
To:        Kris Kennaway <kris@FreeBSD.org>, John Baldwin <jhb@freebsd.org>, freebsd-stable@freebsd.org, Peter Jeremy <peterjeremy@optushome.com.au>
Subject:   Re: Swapping caused by very large (regular) file size
Message-ID:  <20080119175151.GA22860@voi.aagh.net>
In-Reply-To: <20080116182621.GA4260@voi.aagh.net>
References:  <20071203054207.GA1153@aleph.niw.com.au> <4787AAF4.1020905@FreeBSD.org> <20080112033147.GX60060@server.vk2pj.dyndns.org> <200801120005.38972.jhb@freebsd.org> <20080115020316.GA47831@voi.aagh.net> <478C7B04.9080102@FreeBSD.org> <20080116182621.GA4260@voi.aagh.net>

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* Thomas Hurst (tom.hurst@clara.net) wrote:

> * Kris Kennaway (kris@FreeBSD.org) wrote:
> 
> >> Excellent.  I've been seeing this behavior for a long time, mostly on
> >> backup runs (RAID-1 amr SATA -> 1 disk Marvell ata).  It's pretty odd
> >> seeing a system with 8G of memory, 60% of which is just cache, swap
> >> out half a dozen things for no apparant reason.  And to think, people
> >> on FreeNode ##freebsd just insisted I had a misconfigured system ;)
> 
> 7 does indeed seem to resolve this.  Also, no sign of corruption on my
> Marvell 88SX6081, at least during serial read tests.  I'll test with
> a level 0 dump tonight; my writes go via tee to the filesystem and
> sha1(1) so I should pick up any silent corruption.

Doh:

  http://voi.aagh.net/voi.nightsdawn.sf-swap-day.png

Making a 100GB dump of /usr, then making a par2 set results in minor
paging activity all through it.  Running sha1 over the dump has a
similar effect.  It settles around 2.5MB swap now, though; 6 would
quickly settle around 10MB, so it does appear to be improved somewhat;
top isn't showing fetchmail and friends as <swapped> for instance.

This is off a single ata(4) disk, which peaks around 65MB/s.

sha1 file results match that from the dump|tee file|sha1 > file.sha1
at least :)

-- 
Thomas 'Freaky' Hurst
    http://hur.st/



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