lkml.org 
[lkml]   [2009]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: page allocator regression on nommu
On Mon, Aug 31, 2009 at 11:30:56AM +0100, Mel Gorman wrote:
> On Mon, Aug 31, 2009 at 04:48:43PM +0900, Paul Mundt wrote:
> > Hi Mel,
> >
> > It seems we've managed to trigger a fairly interesting conflict between
> > the anti-fragmentation disabling code and the nommu region rbtree. I've
> > bisected it down to:
> >
> > commit 49255c619fbd482d704289b5eb2795f8e3b7ff2e
> > Author: Mel Gorman <mel@csn.ul.ie>
> > Date: Tue Jun 16 15:31:58 2009 -0700
> >
> > page allocator: move check for disabled anti-fragmentation out of fastpath
> >
> > On low-memory systems, anti-fragmentation gets disabled as there is
> > nothing it can do and it would just incur overhead shuffling pages between
> > lists constantly. Currently the check is made in the free page fast path
> > for every page. This patch moves it to a slow path. On machines with low
> > memory, there will be small amount of additional overhead as pages get
> > shuffled between lists but it should quickly settle.
> >
> > which causes death on unpacking initramfs on my nommu board. With this
> > reverted, everything works as expected. Note that this blows up with all of
> > SLOB/SLUB/SLAB.
> >
> > I'll continue debugging it, and can post my .config if it will be helpful, but
> > hopefully you have some suggestions on what to try :-)
> >
>
> Based on the output you have given me, it would appear the real
> underlying cause is that fragmentation caused the allocation to fail.
> The following patch might fix the problem.
>
Unfortunately this has no impact, the same issue occurs.

Note that with 49255c619fbd482d704289b5eb2795f8e3b7ff2e reverted, show_mem()
shows the following:

alloc order 7 for 49000: pages 0c21c000
Mem-Info:
Normal per-cpu:
CPU 0: hi: 0, btch: 1 usd: 0
Active_anon:0 active_file:2 inactive_anon:0
inactive_file:320 unevictable:0 dirty:0 writeback:0 unstable:0
free:2782 slab:0 mapped:0 pagetables:0 bounce:0
Normal free:11128kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:8kB inactive_file:1280kB unevictable:0kB present:16256kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0
Normal: 0*4kB 1*8kB 1*16kB 1*32kB 1*64kB 0*128kB 1*256kB 1*512kB 0*1024kB 1*2048kB 0*4096kB 1*8192kB 0*16384kB 0*32768kB = 11128kB
323 total pagecache pages
4096 pages RAM
662 pages reserved
227 pages shared
289 pages non-shared
0 pages in pagetable cache

while with it applied, consistently:

alloc order 7 for 49000:
modprobe: page allocation failure. order:7, mode:0xd0
...
Mem-Info:
Normal per-cpu:
CPU 0: hi: 0, btch: 1 usd: 0
Active_anon:0 active_file:0 inactive_anon:0
inactive_file:0 unevictable:323 dirty:0 writeback:0 unstable:0
free:2910 slab:0 mapped:0 pagetables:0 bounce:0
Normal free:11640kB min:0kB low:0kB high:0kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:1292kB present:16256kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0
Normal: 252*4kB 245*8kB 238*16kB 152*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB 0*32768kB = 11640kB
323 total pagecache pages
4096 pages RAM
662 pages reserved
226 pages shared
289 pages non-shared
0 pages in pagetable cache
-ENOMEM


\
 
 \ /
  Last update: 2009-08-31 12:45    [W:0.063 / U:2.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site