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RE: XFS memory allocation deadlock in 2.6.38

To: "'Dave Chinner'" <david@xxxxxxxxxxxxx>
Subject: RE: XFS memory allocation deadlock in 2.6.38
From: Sean Noonan <Sean.Noonan@xxxxxxxxxxxx>
Date: Mon, 28 Mar 2011 22:49:33 -0400
Accept-language: en-US
Acceptlanguage: en-US
Cc: "'Michel Lespinasse'" <walken@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Martin Bligh <Martin.Bligh@xxxxxxxxxxxx>, Trammell Hudson <Trammell.Hudson@xxxxxxxxxxxx>, Christos Zoulas <Christos.Zoulas@xxxxxxxxxxxx>, "linux-xfs@xxxxxxxxxxx" <linux-xfs@xxxxxxxxxxx>, Stephen Degler <Stephen.Degler@xxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>
In-reply-to: <20110329015137.GD3008@dastard>
References: <081DDE43F61F3D43929A181B477DCA95639B52FD@xxxxxxxxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B5327@xxxxxxxxxxxxxxxxxxxx> <20110324174311.GA31576@xxxxxxxxxxxxx> <AANLkTikwwRm6FHFtEdUg54NvmKdswQw-NPH5dtq1mXBK@xxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B5349@xxxxxxxxxxxxxxxxxxxx> <BANLkTin0jJevStg5P2hqsLbqMzo3o30sYg@xxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B534E@xxxxxxxxxxxxxxxxxxxx> <20110329015137.GD3008@dastard>
Thread-index: Acvts9zxn6JLCEvNSyWF52bVA/QwTAAB691A
Thread-topic: XFS memory allocation deadlock in 2.6.38
> As it is, the question I'd really like answered is how a machine with
> 48GB RAM can possibly be short of memory when running mmap() on a
> 16GB file.  The error that XFS is throwing indicates that the
> machine cannot allocate a single page of memory, so where has all
> your memory gone, and why hasn't the OOM killer been let off the
> leash?  What is consuming the other 32GB of RAM or preventing it
> from being allocated? 
Here's meminfo while a test was deadlocking.  As you can see, we certainly 
aren't running out of RAM.
# cat /proc/meminfo 
MemTotal:       49551548 kB
MemFree:        44139876 kB
Buffers:            5324 kB
Cached:          4970552 kB
SwapCached:            0 kB
Active:            52772 kB
Inactive:        4960624 kB
Active(anon):      37864 kB
Inactive(anon):        0 kB
Active(file):      14908 kB
Inactive(file):  4960624 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:           4914084 kB
Writeback:             0 kB
AnonPages:         37636 kB
Mapped:          4925460 kB
Shmem:               280 kB
Slab:             223212 kB
SReclaimable:     176280 kB
SUnreclaim:        46932 kB
KernelStack:        3968 kB
PageTables:        35228 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    47073968 kB
Committed_AS:      86556 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      380892 kB
VmallocChunk:   34331773836 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:        2048 kB
DirectMap2M:     2086912 kB
DirectMap1G:    48234496 kB

> Perhaps the output of xfs_bmap -vvp <file> after a successful vs
deadlocked run would be instructive....

I will try to get this tomorrow.


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