Messages in this thread | | | Date | Tue, 23 Nov 2010 15:05:39 +0900 | Subject | Re: [RFC 1/2] deactive invalidated pages | From | Minchan Kim <> |
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On Tue, Nov 23, 2010 at 2:48 PM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Tue, 23 Nov 2010 14:45:15 +0900 Minchan Kim <minchan.kim@gmail.com> wrote: > >> On Tue, Nov 23, 2010 at 2:22 PM, Andrew Morton >> <akpm@linux-foundation.org> wrote: >> > On Tue, 23 Nov 2010 14:23:33 +0900 Minchan Kim <minchan.kim@gmail.com> wrote: >> > >> >> On Tue, Nov 23, 2010 at 2:01 PM, Andrew Morton >> >> <akpm@linux-foundation.org> wrote: >> >> > On Tue, 23 Nov 2010 13:52:05 +0900 Minchan Kim <minchan.kim@gmail.com> wrote: >> >> > >> >> >> >> +/* >> >> >> >> + * Function used to forecefully demote a page to the head of the inactive >> >> >> >> + * list. >> >> >> >> + */ >> >> >> > >> >> >> > This comment is wrong? __The page gets moved to the _tail_ of the >> >> >> > inactive list? >> >> >> >> >> >> No. I add it in _head_ of the inactive list intentionally. >> >> >> Why I don't add it to _tail_ is that I don't want to be aggressive. >> >> >> The page might be real working set. So I want to give a chance to >> >> >> activate it again. >> >> > >> >> > Well.. __why? __The user just tried to toss the page away altogether. __If >> >> > the kernel wasn't able to do that immediately, the best it can do is to >> >> > toss the page away asap? >> >> > >> >> >> If it's not working set, it can be reclaimed easily and it can prevent >> >> >> active page demotion since inactive list size would be big enough for >> >> >> not calling shrink_active_list. >> >> > >> >> > What is "working set"? __Mapped and unmapped pagecache, or are you >> >> > referring solely to mapped pagecache? >> >> >> >> I mean it's mapped by other processes. >> >> >> >> > >> >> > If it's mapped pagecache then the user was being a bit silly (or didn't >> >> > know that some other process had mapped the file). __In which case we >> >> > need to decide what to do - leave the page alone, deactivate it, or >> >> > half-deactivate it as this patch does. >> >> >> >> >> >> What I want is the half-deactivate. >> >> >> >> Okay. We will use the result of invalidate_inode_page. >> >> If fail happens by page_mapped, we can do half-deactivate. >> >> But if fail happens by dirty(ex, writeback), we can add it to tail. >> >> Does it make sense? >> > >> > Spose so. __It's unobvious. >> > >> > If the page is dirty or under writeback then reclaim will immediately >> > move it to the head of the LRU anyway. __But given that the user has >> >> Why does it move into head of LRU? >> If the page which isn't mapped doesn't have PG_referenced, it would be >> reclaimed. > > If it's dirty or under writeback it can't be reclaimed!
I see your point. And it's why I add it to head of inactive list.
> >> > just freed a bunch of pages with invalidate(), it's unlikely that >> > reclaim will be running soon. >> >> If reclaim doesn't start soon, it's good. That's because we have a >> time to activate it and >> when reclaim happens, reclaimer can reclaim pages easily. >> >> If I don't understand your point, could you elaborate on it? > > If reclaim doesn't happen soon and the page was dirty or under > writeback (and hence unreclaimable) then there's a better chance that > it _will_ be reclaimable by the time reclaim comes along and has a look > at it. Yes, that's good. > > And a note to Mel: this is one way in which we can get significant > (perhaps tremendous) numbers of dirty pages coming off the tail of the > LRU, and hence eligible for pageout() treatment. >
I think you agree my as-is approach. Right? Then, could you revert your fixlet? I will add additional description with your fix.
-- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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