Messages in this thread | | | Date | Wed, 28 Sep 2011 01:19:50 -0700 | Subject | Re: [PATCH 6/9] kstaled: rate limit pages scanned per second. | From | Michel Lespinasse <> |
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On Wed, Sep 28, 2011 at 1:13 AM, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Tue, 27 Sep 2011 17:49:04 -0700 > Michel Lespinasse <walken@google.com> wrote: > >> Scan some number of pages from each node every second, instead of trying to >> scan the entime memory at once and being idle for the rest of the configured >> interval. >> >> In addition to spreading the CPU usage over the entire scanning interval, >> this also reduces the jitter between two consecutive scans of the same page. >> >> >> Signed-off-by: Michel Lespinasse <walken@google.com> > > Does this scan thread need to be signle thread ?
It tends to perform worse if we try making it multithreaded. What happens is that the scanning threads call page_referenced() a lot, and if they both try scanning pages that belong to the same file that causes the mapping's i_mmap_mutex lock to bounce. Same things happens if they try scanning pages that belong to the same anon VMA too.
-- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.
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