Messages in this thread Patch in this message | | | Date | Thu, 20 May 2010 07:20:42 -0400 | From | Larry Woodman <> | Subject | RFC: dirty_ratio back to 40% |
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We've seen multiple performance regressions linked to the lower(20%) dirty_ratio. When performing enough IO to overwhelm the background flush daemons the percent of dirty pagecache memory quickly climbs to the new/lower dirty_ratio value of 20%. At that point all writing processes are forced to stop and write dirty pagecache pages back to disk. This causes performance regressions in several benchmarks as well as causing a noticeable overall sluggishness. We all know that the dirty_ratio is an integrity vs performance trade-off but the file system journaling will cover any devastating effects in the event of a system crash.
Increasing the dirty_ratio to 40% will regain the performance loss seen in several benchmarks. Whats everyone think about this???
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diff --git a/mm/page-writeback.c b/mm/page-writeback.c index ef27e73..645a462 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -78,7 +78,7 @@ int vm_highmem_is_dirtyable; /* * The generator of dirty data starts writeback at this percentage */ -int vm_dirty_ratio = 20; +int vm_dirty_ratio = 40; /* * vm_dirty_bytes starts at 0 (disabled) so that it is a function of
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