Messages in this thread | | | From | Matthias Wolle <> | Subject | Re: LowFree/LowMem problem | Date | Fri, 25 Jan 2008 02:45:34 +0100 |
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On Thursday 24 January 2008 08:16 Andi Kleen wrote: > Do you perhaps have a kernel compiled without CONFIG_HIGHPTE? Normally > __pte_alloc should be able to allocate highmem unless that option is > not set. Before HIGHPTE was implemented running out of low memory > due to page tables was pretty common.
The kernel from 17th Jan 2008 didn't have CONFIG_HIGHPTE enabled. Yesterday we checked a 2.6.23.14 kernel with CONFIG_HIGHPTE enabled. The 4GB test machine showed the same fast low memory reducing effect. LowFree stopped at 400MB like without CONFIG_HIGHPTE. A 2GB machine had a limit of 690MB LowFree. The difference of LowTotal and LowFree is shown as used memory. In case of the 4GB machine, this means I have 400MB used memory which is not related to any process. I hope this helps. I can't test on the 16GB RAM machines anymore, because they are working productive now.
> BTW the ultimate fix for most lowmem problems is to go 64bit
We switched back to the distribution default 2.6.18-bigmem kernel of debian which doesn't have this problem. On this kernel the test script has no effect to the low memory.
Regards Matthias
On Thursday 24 January 2008 08:16 Andi Kleen wrote: > Matthias Wolle <Matthias.Wolle@gmx.de> writes: > > Jan 17 23:31:58 franklin72 kernel: sshd invoked oom-killer: > > gfp_mask=0xd0, order=0, oomkilladj=0 Jan 17 23:31:58 franklin72 kernel: > > cat invoked oom-killer: gfp_mask=0x84d0, order=0, oomkilladj=0 Jan 17 > > 23:31:58 franklin72 kernel: [<c014af39>] out_of_memory+0x69/0x1a4 Jan 17 > > 23:31:58 franklin72 kernel: [<c014c588>] __alloc_pages+0x20a/0x291 Jan > > 17 23:31:58 franklin72 kernel: [<c0153618>] __pte_alloc+0x11/0x94 > > Do you perhaps have a kernel compiled without CONFIG_HIGHPTE? Normally > __pte_alloc should be able to allocate highmem unless that option is > not set. Before HIGHPTE was implemented running out of low memory > due to page tables was pretty common. > > BTW the ultimate fix for most lowmem problems is to go 64bit > > -Andi
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