>
> On Thu, May 20, 2010 at 07:20:42AM -0400, Larry Woodman wrote:
> > 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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