On Tue, 2009-12-01 at 21:20 -0500, Rik van Riel wrote:

This is reasonable, except for the fact that pages that are moved
to the inactive list without having the referenced bit cleared are
guaranteed to be moved back to the active list.

You'll be better off without that excess list movement, by simply
moving pages directly back onto the active list if the trylock
fails.

The attached patch addresses this issue by changing page_check_address()
to return -1 if the spin_trylock() fails and page_referenced_one() to
return 1 in that path so the page gets moved back to the active list.

Also, BTW, check this out: an 8-CPU/16GB system running AIM 7 Compute
has 196491 isolated_anon pages.  This means that ~6140 processes are
somewhere down in try_to_free_pages() since we only isolate 32 pages at
a time, this is out of 9000 processes...


---------------------------------------------------------------------
active_anon:2140361 inactive_anon:453356 isolated_anon:196491
 active_file:3438 inactive_file:1100 isolated_file:0
 unevictable:2802 dirty:153 writeback:0 unstable:0
 free:578920 slab_reclaimable:49214 slab_unreclaimable:93268
 mapped:1105 shmem:0 pagetables:139100 bounce:0

Node 0 Normal free:1647892kB min:12500kB low:15624kB high:18748kB 
active_anon:7835452kB inactive_anon:785764kB active_file:13672kB 
inactive_file:4352kB unevictable:11208kB isolated(anon):785964kB 
isolated(file):0kB present:12410880kB mlocked:11208kB dirty:604kB 
writeback:0kB mapped:4344kB shmem:0kB slab_reclaimable:177792kB 
slab_unreclaimable:368676kB kernel_stack:73256kB pagetables:489972kB 
unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0

202895 total pagecache pages
197629 pages in swap cache
Swap cache stats: add 6954838, delete 6757209, find 1251447/2095005
Free swap  = 65881196kB
Total swap = 67354616kB
3997696 pages RAM
207046 pages reserved
1688629 pages shared
3016248 pages non-shared