what process is eating my swap? -> SOLVED

[Greg 'groggy' Lehey]

On Monday, 12 May 2003 at 12:16:35 +0200, Stijn Hoop wrote:
> On Fri, May 09, 2003 at 04:12:00PM +0200, Stijn Hoop wrote:
>> My swapspace is 99% used, but I can't find a way to figure out what process is
>> using it. top & ps don't seem to list swap usage of processes, and systat
>> -swap only lists the fact that 99% is in use.
>
> [snip]
>
>> - I'm using vinum for two RAID-5 arrays on 8 ATA disks, and was
>>   rsync'ing from one to the other at the time the kernel complained
>>   about lack of swapspace:
>>
>> [stijn at sandcat] </> dmesg | grep swap
>> swap_pager_getswapspace: failed
>> pid 33932 (rsync), uid 0, was killed: out of swap space
>>
>>   Could vinum somehow 'leak' swap space? My swap partition is on a regular
>>   SCSI disk, not on a vinum volume, so this seems farfetched but I'm a bit
>>   at a loss here.
>>
>> Anyone have any clue? I need to have a bit of virtual memory on this
>> machine...
>
> I figured it out, and I thought I'd let you know what the problem was:
>
> -> don't _EVER_ build a vinum RAID-5 with a blocksize of 512 bytes (and try
>    to do something with it)

This is good advice, but I don't think it's the cause of your swap
problem.  Vinum doesn't use *any* swap.  I thought that it was
possibly something to do with rsync, so I tried it anyway (boy, is it
slow!), and confirmed that it didn't use any swap.  I did have up to
781 concurrently active requests, which could have used a lot of
kernel memory, but that wouldn't have affected swap.

> Actually, that wasn't my intention of course but I forgot to end my
> plex size While doing the rsync to this RAID-5 it was, I think, the
> buffer cache that couldn't keep up with the number of blocks vinum
> had to read/write, and so my virtual memory kept filling up.

Buffer cache isn't swap backed.

> At least, now that I've rebuild the RAID with the proper blocksize,
> I'm not running into swap space problems anymore.

That may just be a coincidence.

> Greg, does it ever make any sense to build a RAID with a blocksize <
> 128k?  The manpage says it doesn't;

And I wrote the man page :-)

> maybe vinum could issue a warning while creating such a plex?

That's a possibility.

Greg
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