Messages in this thread | | | Date | Mon, 21 Jul 2008 09:09:26 +0900 | From | "KOSAKI Motohiro" <> | Subject | Re: [PATCH -mm] mm: more likely reclaim MADV_SEQUENTIAL mappings |
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Hi Johannes,
> File pages accessed only once through sequential-read mappings between > fault and scan time are perfect candidates for reclaim. > > This patch makes page_referenced() ignore these singular references and > the pages stay on the inactive list where they likely fall victim to the > next reclaim phase. > > Already activated pages are still treated normally. If they were > accessed multiple times and therefor promoted to the active list, we > probably want to keep them. > > Benchmarks show that big (relative to the system's memory) > MADV_SEQUENTIAL mappings read sequentially cause much less kernel > activity. Especially less LRU moving-around because we never activate > read-once pages in the first place just to demote them again. > > And leaving these perfect reclaim candidates on the inactive list makes > it more likely for the real working set to survive the next reclaim > scan.
looks good to me. Actually, I made similar patch half year ago.
in my experience, - page_referenced_one is performance critical point. you should test some benchmark. - its patch improved mmaped-copy performance about 5%. (Of cource, you should test in current -mm. MM code was changed widely)
So, I'm looking for your test result :)
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