Messages in this thread | | | Date | Tue, 23 Nov 2004 10:09:34 +1100 | From | Nick Piggin <> | Subject | Re: deferred rss update instead of sloppy rss |
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Christoph Lameter wrote: > On Mon, 22 Nov 2004, Andrew Morton wrote: > > >>>The page fault code only increments rss. For larger transactions that >>>increase / decrease rss significantly the page_table_lock is taken and >>>mm->rss is updated directly. So no >>>gross inaccuracies can result. >> >>Sure. Take a million successive pagefaults and mm->rss is grossly >>inaccurate. Hence my suggestion that it be spilled into mm->rss >>periodically. > > > It is spilled into mm->rss periodically. That is the whole point of the > patch. > > The timer tick occurs every 1 ms. The maximum pagefault frequency that I > have seen is 500000 faults /second. The max deviation is therefore > less than 500 (could be greater if page table lock / mmap_sem always held > when the tick occurs).
You could imagine a situation where something pagefaults and sleeps in lock-step with the timer though. Theoretical problem only?
I think that by the time you get the spilling code in, the mm-list method will be looking positively elegant!
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