From: Dave Chinner <david@fromorbit.com>
To: "Al Lau (alau2)" <alau2@cisco.com>
Cc: "xfs@oss.sgi.com" <xfs@oss.sgi.com>
Subject: Re: mkfs.xfs -n size=65536
Date: Tue, 13 Oct 2015 14:33:04 +1100 [thread overview]
Message-ID: <20151013033304.GL27164@dastard> (raw)
In-Reply-To: <8a1b26a3b869448e805485c529c447a4@XCH-ALN-020.cisco.com>
On Tue, Oct 13, 2015 at 01:39:13AM +0000, Al Lau (alau2) wrote:
> Have a 3 TB file. Logically divide into 1024 sections. Each
> section has a process doing dd to a randomly selected 4K block in
> a loop. Will this test case eventually cause the extent
> fragmentation that lead to the kmem_alloc message?
>
> dd if=/var/kmem_alloc/junk of=/var/kmem_alloc/fragmented obs=4096 bs=4096 count=1 seek=604885543 conv=fsync,notrunc oflag=direct
If you were loking for a recipe to massively fragment a file, then
you found it. And, yes, when you start to get millions of extents in
a file such as this workload will cause, you'll start having memory
allocation problems.
But I don't think that sets the GFP_ZERO flag anywhere, so that's
not necessarily where the memroy shortage is coming from. I just
committed some changes to the dev tree that allow for more detailed
information from this allocation error point to be obtained -
perhaps if woul dbe worthwhile trying a kernel build form the
current for-next tree and turning the error level up to 11?
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2015-10-13 3:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-09 22:40 mkfs.xfs -n size=65536 Al Lau (alau2)
2015-10-13 0:23 ` Dave Chinner
2015-10-13 1:39 ` Al Lau (alau2)
2015-10-13 3:33 ` Dave Chinner [this message]
2015-10-13 3:42 ` Al Lau (alau2)
2015-10-13 3:55 ` Al Lau (alau2)
2015-10-13 4:30 ` Dave Chinner
2015-10-13 7:28 ` Al Lau (alau2)
2015-10-13 8:25 ` Dave Chinner
2015-11-06 2:06 ` Al Lau (alau2)
2015-10-13 4:04 ` Al Lau (alau2)
2015-10-13 22:05 ` Al Lau (alau2)
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