Swapping caused by very large (regular) file size

Kris Kennaway kris at FreeBSD.org
Sat Jan 19 11:32:45 PST 2008

Thomas Hurst wrote:
> * 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.
> 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 :)

I don't understand your test procedure, can you elaborate?


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