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    SubjectRFC: dirty_ratio back to 40%
    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???


    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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      Last update: 2010-05-20 13:27    [W:0.019 / U:21.632 seconds]
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