Messages in this thread | | | Date | Wed, 10 Jul 2002 18:34:22 +0200 | From | Andrea Arcangeli <> | Subject | Re: Terrible VM in 2.4.11+ again? |
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On Tue, Jul 09, 2002 at 12:48:08PM +0200, Lukas Hejtmanek wrote: > On Tue, Jul 09, 2002 at 12:58:16AM +0200, J.A. Magallon wrote: > > Seriously, if you have that kind of problems, take the -aa kernel and use it. > > I use it regularly and it behaves as one would expect, and fast. > > And please, report your results... > > I've tried 2.4.19rc1aa2, it swaps even when I have 512MB ram and xcdroast with > scsi-ide emulation cd writer reports to syslog: > Jul 9 12:45:02 hell kernel: __alloc_pages: 3-order allocation failed > (gfp=0x20/0) > Jul 9 12:45:02 hell kernel: __alloc_pages: 3-order allocation failed > (gfp=0x20/0) > Jul 9 12:45:02 hell kernel: __alloc_pages: 2-order allocation failed > (gfp=0x20/0) > Jul 9 12:45:02 hell kernel: __alloc_pages: 1-order allocation failed > (gfp=0x20/0) > Jul 9 12:45:02 hell kernel: __alloc_pages: 0-order allocation failed > (gfp=0x20/0) > > Am I something missing?
you may want to reproduce with vm_debug set to 1, but I'm pretty sure it's a scsi generic issue, they are allocating ram with GFP_ATOMIC, and they may eventually fail if kswapd cannot keep up with the other GFP_ATOMIC allocations. They should use GFP_NOIO, with -aa it won't even try to unmap pages. It will just try to shrink clean cache and it should work fine for the above purpose where the allocation needs low latency (the local_pages per-task ensures their work won't be stolen by the GFP_ATOMIC users). I asked for that change some time ago but it never happened apparently. However I assume the sr layer tried some more after failing, sg has a quite large queue so some delay isn't fatal, and you can probably safely ignore the above messages, they're just warnings for you. nevertheless GFP_NOIO would make the allocations more reliable.
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