Messages in this thread | | | Date | Thu, 4 Dec 2008 00:12:15 +0900 | From | "KOSAKI Motohiro" <> | Subject | Re: [PATCH] vmscan: improve reclaim throuput to bail out patch |
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>> I evaluate rvr bailout and skip-freeing patch in this week conteniously. >> I'd like to dump first output here. >> >> >> >> Rik, could you please review following? >> == >> vmscan bail out patch move nr_reclaimed variable to struct scan_control. >> Unfortunately, indirect access can easily happen cache miss. >> More unfortunately, Some architecture (e.g. ia64) don't access global >> variable so fast. > > That is amazing. Especially considering that the scan_control > is a local variable on the stack.
Ahhhhh, I did want to write "indirect access(or likes global variables)", but my brain was sucked. sorry.
I'll post description fixed version soon. thanks.
>> if heavy memory pressure happend, that's ok. >> cache miss already plenty. it is not observable. >> >> but, if memory pressure is lite, performance degression is obserbable. > >> about 4-5% degression. >> >> Then, this patch introduce temporal local variable. > >> OK. the degression is disappeared. > > I can't argue with the numbers, though :) > > Maybe all the scanning we do ends up evicting the cache lines > with the scan_control struct in it from the fast part of the > CPU cache?
Yeah, I think so.
> >> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > > Acked-by: Rik van Riel <riel@redhat.com>
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