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Date: Sat, 19 Jan 2008 21:28:23 +0100
From: Kris Kennaway <kris@FreeBSD.org>
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To: Kris Kennaway <kris@FreeBSD.org>, John Baldwin <jhb@freebsd.org>, 
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Subject: Re: Swapping caused by very large (regular) file size
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Thomas Hurst wrote:
> * Kris Kennaway (kris@FreeBSD.org) wrote:
> 
>> I don't understand your test procedure, can you elaborate?
> 
> The spikes from last night are from:
> 
> (/sbin/dump -$level -LuaC128 -f - $fs | /usr/bin/tee ${target} |
> /sbin/sha1 > ${target}.sha1)
> 
> Followed by:
> 
> nice -n 19 /home/freaky/bin/par2 c -t+ -r5 -m256 ${target}
> 
> Graphs from this run clearly slow a modest amount of paging activity
> while it occurs; you can see the other graphs here:
> 
>   http://voi.aagh.net/backupmunin/
> 
> More simply, it can be reproduced by doing this:
> 
> -# swapoff -a # clear swap
> -# swapon -a
> -# top |grep -A1 Mem
> Mem: 1371M Active, 5727M Inact, 416M Wired, 271M Cache, 214M Buf, 124M
> Free
> Swap: 10G Total, 10G Free
> -# ls -l voi_20080119_#usr.dmp.0
> -rw-r--r--    1 root     wheel    106527672320 Jan 19 05:27
> voi_20080119_#usr.dmp.0
> -# cat voi_20080119_#usr.dmp.0 >/dev/null &
> -% sleep 20 && top |grep -A1 Mem
> Mem: 1407M Active, 5789M Inact, 431M Wired, 272M Cache, 214M Buf, 8580K
> Free
> Swap: 10G Total, 400K Used, 10G Free
> 
> The system's occasionally deciding to swap pages out rather than recycle
> something from the huge pool of inactive/cache memory (which atm will be
> mostly cached pages from this file, since this is my second test run;
> the first took longer to ramp up).
> 
> -% uname -a
> FreeBSD voi.nightsdawn.sf 7.0-RC1 FreeBSD 7.0-RC1 #0: Wed Jan 16
> 14:56:50 GMT 2008

Thanks, I will try to reproduce.

Kris