On 2010-06-17 13:39, Richard Kennedy wrote: > On Wed, 2010-06-16 at 20:54 +0200, Peter Zijlstra wrote: >> On Mon, 2010-06-14 at 15:44 +0100, Richard Kennedy wrote: >>>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c >>>> index 2fdda90..315dd04 100644 >>>> --- a/mm/page-writeback.c >>>> +++ b/mm/page-writeback.c >>>> @@ -144,7 +144,7 @@ static int calc_period_shift(void) >>>> else >>>> dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) / >>>> 100; >>>> - return 2 + ilog2(dirty_total - 1); >>>> + return ilog2(dirty_total - 1) - 4; >>>> } >> >> IIRC I suggested similar things in the past and all we needed to do was >> find people doing the measurements on different bits of hardware or so.. >> >> I don't have any problems with the approach, all we need to make sure is >> that we never return 0 or a negative number (possibly ensure a minimum >> positive shift value). > > Yep that sounds reasonable. would minimum shift of 4 be ok ? > > something like > > max ( (ilog2(dirty_total - 1)- 4) , 4); > > Unfortunately volunteers don't seem to be leaping out of the woodwork, > maybe Andrew could be persuaded to try this in his tree for a while and > see if any one squeaks ? I'm pretty sure that most volunteers are curious what to actually test, so they shy away from it. If you added a good explanation of an easy way to test the before and after, then it would be more approachable. I'll give it a spin here. -- Jens Axboe -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>