Messages in this thread | | | Date | Tue, 24 Mar 2015 10:45:45 +0300 | From | Vladimir Davydov <> | Subject | Re: [PATCH 0/3] idle memory tracking |
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On Wed, Mar 18, 2015 at 11:44:33PM +0300, Vladimir Davydov wrote: > Usage: > > 1. Write 1 to /proc/sys/vm/set_idle. > > This will set the IDLE flag for all user pages. The IDLE flag is cleared > when the page is read or the ACCESS/YOUNG bit is cleared in any PTE pointing > to the page. It is also cleared when the page is freed. > > 2. Wait some time. > > 3. Write 6 to /proc/PID/clear_refs for each PID of interest. > > This will clear the IDLE flag for recently accessed pages. > > 4. Count the number of idle pages as reported by /proc/kpageflags. One may use > /proc/PID/pagemap and/or /proc/kpagecgroup to filter pages that belong to a > certain application/container.
Any more thoughts on this? I am particularly interested in the user interface. I think that /proc/kpagecgroup is OK, but I have my reservations about using /proc/sys/vm/set_idle and /proc/PID/clear_refs for setting and clearing the idle flag. The point is it is impossible to scan memory for setting/clearing page idle flags in the background with some predefined rate - one has to scan it all at once, which might result in CPU load spikes on huge machines with TBs of RAM. May be, we'd better introduce /proc/sys/vm/{set_idle,clear_refs_idle}, which would receive pfn range to set/clear idle flags?
Any thoughts/ideas are more than welcome.
Thanks, Vladimir
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