Messages in this thread | | | Subject | Re: Order 0 page allocation failure under heavy I/O load | From | Peter Zijlstra <> | Date | Mon, 27 Oct 2008 09:04:56 +0100 |
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On Mon, 2008-10-27 at 17:22 +1100, Dave Chinner wrote: > On Mon, Oct 27, 2008 at 06:47:31AM +0100, Claudio Martins wrote: > > On Sunday 26 October 2008, Dave Chinner wrote: > > > > > The host will hang for tens of seconds at a time with both CPU cores > > > pegged at 100%, and eventually I get this in dmesg: > > > > > > [1304740.261506] linux: page allocation failure. order:0, mode:0x10000 > > > [1304740.261516] Pid: 10705, comm: linux Tainted: P 2.6.26-1-amd64
> No, because I've found the XFS bug the workload was triggering so > I don't need to run it anymore. > > I reported the problem because it appears that we've reported an > allocation failure without very much reclaim scanning (64 pages in > DMA zone, 0 pages in DMA32 zone), and there is apparently pages > available for allocation in the DMA zone: > > 1304740.262136] Node 0 DMA: 160*4kB 82*8kB 32*16kB 11*32kB 8*64kB 4*128kB 3*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB = 8048kB > > So it appears that memory reclaim has not found the free pages it > apparently has available.... > > Fundamentally, I/O from a single CPU to a single disk on a machine > with 2GB RAM should not be able to cause allocation failures at all, > especially when the I/O is pure data I/O to a single file. Something > in the default config is busted if I can do that, and that's why > I reported the bug.
The allocation is 'mode:0x10000', which is __GFP_NOMEMALLOC. That means the allocation doesn't have __GFP_WAIT, so it cannot do reclaim, it doesn't have __GFP_HIGH so it can't access some emergency reserves.
The DMA stuff is special, and part of it is guarded for anything but __GFP_DMA allocations.
You just ran the system very low on memory, and then tried an allocation that can't do anything about it.. I don't find it very surprising it fails.
The 'bug' if any, is having such a poor allocation within your IO path. Not something to blame on the VM.
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