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Re: 10GB memorys occupied by XFS

To: daiguochao <dx-wl@xxxxxxx>
Subject: Re: 10GB memorys occupied by XFS
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 11 Apr 2014 14:26:25 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1397184044761-35016.post@xxxxxxxxxxxxx>
References: <1396596386220-35015.post@xxxxxxxxxxxxx> <1397184044761-35016.post@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Apr 10, 2014 at 07:40:44PM -0700, daiguochao wrote:
> Dear Stan, I can't send email to you.So I leave a message here.I hope not to
> bother you.
> Thank you for your kind assistance.
> In accordance with your suggestion, we executed "echo 3 >
> /proc/sysm/drop_caches" for trying to release vfs dentries and inodes.
> Really,
> our lost memory came back. But we learned that the memory of vfs dentries
> and inodes is distributed from slab. Please check our system "Slab:  509708
> kB" from /proc/meminfo, and it seems only be took up 500MB and xfs_buf take
> up 450MB among.

That's where your memory is - in metadata buffers. The xfs_buf slab
entries are just the handles - the metadata pages in the buffers
usually take much more space and it's not accounted to the slab
cache nor the page cache.

Can you post the output of /proc/slabinfo, and what is the output of
xfs_info on the filesystem in question? Also, a description of your
workload that is resulting in large amounts of cached metadata
buffers but no inodes or dentries would be helpful.


Dave Chinner

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