Swapping caused by very large (regular) file size

Thomas Hurst tom.hurst at clara.net
Sat Jan 19 09:51:55 PST 2008

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

> * Kris Kennaway (kris at 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.



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

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