From: Eric Sandeen <sandeen@sandeen.net>
To: xfs@oss.sgi.com
Subject: Re: Request for information on bloated writes using Swift
Date: Tue, 2 Feb 2016 20:47:24 -0600 [thread overview]
Message-ID: <56B16A3C.1030207@sandeen.net> (raw)
In-Reply-To: <CAFHL4X1JU02LFYntkqhYg1N++ZU46ML3v5higo1nRsPyoZxL5A@mail.gmail.com>
On 2/2/16 4:32 PM, Dilip Simha wrote:
> Hi,
>
> I have a question regarding speculated preallocation in XFS, w.r.t
> kernel version: 3.16.0-46-generic. I am using Swift version: 1.0 and
> mkfs.xfs version 3.2.1
>
> When I write a 256KiB file to Swift, I see that the underlying XFS
> uses 3x the amount of space/blocks to write that data. Upon
> performing detailed experiments, I see that when Swift uses fallocate
> (default approach), XFS doesn't reclaim the preallocated blocks that
> XFS allocated. Swift fallocate doesn't exceed the body size(256
> KiB).
>
> Interestingly, when either allocsize=4k or when swift doesn't use
> fallocate, XFS doesn't consume additional space.
>
> Can you please let me know if this is a known bug and if its fixed in
> the later versions?
Can you clarify the exact sequence of events?
i.e. -
xfs_io -f -c "fallocate 0 256k" -c "pwrite 0 256k" somefile
leads to unreaclaimed preallocation, while
xfs_io -f -c "pwrite 0 256k" somefile
does not? Or is it some other sequence? I don't have a
3.16 handy to test, but if you can describe it in more detail
that'd help. Some of this is influenced by fs geometry, too
so xfs_info output would be good, along with any mount options
you might be using.
Are you preallocating with or without KEEP_SIZE?
-Eric
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next prev parent reply other threads:[~2016-02-03 2:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-02 22:32 Request for information on bloated writes using Swift Dilip Simha
2016-02-03 2:47 ` Eric Sandeen [this message]
2016-02-03 3:40 ` Dilip Simha
2016-02-03 3:42 ` Dilip Simha
2016-02-03 6:37 ` Dave Chinner
2016-02-03 7:09 ` Dilip Simha
2016-02-03 8:30 ` Dave Chinner
2016-02-03 15:02 ` Eric Sandeen
2016-02-03 21:51 ` Dave Chinner
2016-02-03 22:43 ` Dilip Simha
2016-02-03 23:28 ` Dave Chinner
2016-02-04 6:16 ` Dilip Simha
2016-02-03 16:10 ` Dilip Simha
2016-02-03 16:15 ` Dilip Simha
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