Date: Sun, 05 Jan 2014 13:13:17 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Vladimir Sharun <atz@ukr.net>, Current FreeBSD <freebsd-current@FreeBSD.org> Subject: Re: ARC "pressured out", how to control/stabilize ? (reformatted to text/plain) Message-ID: <52C93E4D.1050100@FreeBSD.org> In-Reply-To: <1388839805.123581691.q97ijp8l@frv45.ukr.net> References: <1388839805.123581691.q97ijp8l@frv45.ukr.net>
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on 04/01/2014 14:50 Vladimir Sharun said the following:
[snip]
> ARC: 28G Total, 2085M MFU, 20G MRU, 29M Anon, 1858M Header, 3855M Other
[snip]
> ITEM SIZE LIMIT USED FREE REQ FAIL SLEEP
[snip]
> zio_data_buf_131072: 131072, 0, 488217, 9,287155442, 0, 0
I noticed a particular discrepancy between reported ARC usage and sizes of UMA
zones used by ZFS code:
488217 * 131072 = ~59GB right there.
There are several possibilities for this discrepancy:
- bad accounting or reporting of ARC stats
- those 128K buffers being used in a special way and thus not accounted as ARC
- some sort of resource leak
You could try to use DTrace to gather the stacks of all code paths that lead to
allocation of those buffers. Something like:
fbt::zio_data_buf_alloc:entry
/arg0 == 131072/
{
@[stack()] = count();
}
This could be a start for understanding the issue.
--
Andriy Gapon
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