From: Mel Gorman <mgorman@suse.de>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Minchan Kim <minchan.kim@gmail.com>,
Dave Jones <davej@redhat.com>, Jan Kara <jack@suse.cz>,
Andy Isaacson <adi@hexapodia.org>,
Johannes Weiner <jweiner@redhat.com>,
Rik van Riel <riel@redhat.com>, Nai Xia <nai.xia@gmail.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 11/11] mm: Isolate pages for immediate reclaim on their own LRU
Date: Tue, 20 Dec 2011 09:55:44 +0000 [thread overview]
Message-ID: <20111220095544.GP3487@suse.de> (raw)
In-Reply-To: <20111220071026.GA19025@barrios-laptop.redhat.com>
On Tue, Dec 20, 2011 at 04:10:26PM +0900, Minchan Kim wrote:
> > > > * Writeback is about to end against a page which has been marked for immediate
> > > > * reclaim. If it still appears to be reclaimable, move it to the tail of the
> > > > * inactive list.
> > > > */
> > > > void rotate_reclaimable_page(struct page *page)
> > > > {
> > > > + struct zone *zone = page_zone(page);
> > > > + struct list_head *page_list;
> > > > + struct pagevec *pvec;
> > > > + unsigned long flags;
> > > > +
> > > > + page_cache_get(page);
> > > > + local_irq_save(flags);
> > > > + __mod_zone_page_state(zone, NR_IMMEDIATE, -1);
> > > > +
> > >
> > > I am not sure underflow never happen.
> > > We do SetPageReclaim at several places but dont' increase NR_IMMEDIATE.
> > >
> >
> > In those cases, we do not move the page to the immedate list either.
>
> That's my concern.
> We didn't move the page to immediate list but set SetPageReclaim. It means
> we don't increate NR_IMMEDIATE.
> If end_page_writeback have called that page, rotate_reclimable_page would be called.
> Eventually, __mod_zone_page_state(zone, NR_IMMEDIATE, -1) is called.
> But I didn't look into the code yet for confirming it's possbile or not.
>
Ah, now I see your concern. The key is that they get moved to the
immediate LRU later although it is not obvious. This should be double
checked but when I was implementing this, I looked at the different
places that called SetPageReclaim.
mm/swap.c:lru_deactivate_fn() calls SetPageReclaim but also moves the
page to the immediate LRU list so no problem with accounting
there.
mm/vmscan.c:pageout() calls SetPageReclaim but does not move the page
explicitly as such. Instead, it gets picked up by
putback_lru_pages() later which checks for inactive LRU pages
that are marked PageReclaim and selects the immediate LRU in
this case. The counter gets incremented for the appropriate
LRU list by __add_page_to_lru_list(). Even if we do have
an active page with PageReclaim set, it should not cause an
accounting difficulty
mm/vmscan.c:shrink_page_list() calls SetPageReclaim but like pageout(),
it gets picked up by putback_lru_pages() later
Did I miss anything?
> > During one test I was recording /proc/vmstat every 10 seconds and never
> > saw an underflow.
>
> If it's very rare, it would be very hard to see it.
>
But once it happened, I would not expect it to recover. The nr_immediate
value usually reads as 0.
> > > > <SNIP>
> > > > static void update_page_reclaim_stat(struct zone *zone, struct page *page,
> > > > @@ -475,6 +532,13 @@ static void lru_deactivate_fn(struct page *page, void *arg)
> > > > * is _really_ small and it's non-critical problem.
> > > > */
> > > > SetPageReclaim(page);
> > > > +
> > > > + /*
> > > > + * Move to the LRU_IMMEDIATE list to avoid being scanned
> > > > + * by page reclaim uselessly.
> > > > + */
> > > > + list_move_tail(&page->lru, &zone->lru[LRU_IMMEDIATE].list);
> > > > + __mod_zone_page_state(zone, NR_IMMEDIATE, 1);
> > >
> > > It mekes below count of PGDEACTIVATE wrong in lru_deactivate_fn.
> > > Before this patch, all is from active to inacive so it was right.
> > > But with this patch, it can be from acdtive to immediate.
> > >
> >
> > I do not quite understand. PGDEACTIVATE is incremented if the page was
> > active and this is checked before the move to the immediate LRU. Whether
> > it moves to the immediate LRU or the end of the inactive list, it is
> > still a deactivation. What's wrong with incrementing the count if it
>
> Hmm, I have thought deactivation is only from active to deactive.
This is a matter of definition really. The page is going from active
to inactive. The immediate list is similar to the inactive list in
this case, at least from a deactivation point of view.
> I might be wrong but if we perhaps move page from active to unevictable list,
> is it deactivation, too?
I would consider it a deactivate if PageActive got cleared. Here we are
talking about the lru_deactivate_fn function. Whether it moves to the
immediate list or the end of the inactive list, the page is being
deactivated.
> Maybe we need consistent count.
>
In this case, I think we are being consistent. The page is deactivated,
we increase the PFDEACTIVATE counter.
Thanks very much for reviewing this closely, I appreciate it.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2011-12-20 9:55 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-14 15:41 [PATCH 0/11] Reduce compaction-related stalls and improve asynchronous migration of dirty pages v6 Mel Gorman
2011-12-14 15:41 ` [PATCH 01/11] mm: compaction: Allow compaction to isolate dirty pages Mel Gorman
2011-12-14 15:41 ` [PATCH 02/11] mm: compaction: Use synchronous compaction for /proc/sys/vm/compact_memory Mel Gorman
2011-12-14 15:41 ` [PATCH 03/11] mm: vmscan: Check if we isolated a compound page during lumpy scan Mel Gorman
2011-12-15 23:21 ` Rik van Riel
2011-12-14 15:41 ` [PATCH 04/11] mm: vmscan: Do not OOM if aborting reclaim to start compaction Mel Gorman
2011-12-15 23:36 ` Rik van Riel
2011-12-14 15:41 ` [PATCH 05/11] mm: compaction: Determine if dirty pages can be migrated without blocking within ->migratepage Mel Gorman
2011-12-16 3:32 ` Rik van Riel
2011-12-16 23:20 ` Andrew Morton
2011-12-17 3:03 ` Nai Xia
2011-12-17 3:26 ` Andrew Morton
2011-12-19 11:05 ` Mel Gorman
2011-12-19 13:12 ` nai.xia
2011-12-14 15:41 ` [PATCH 06/11] mm: compaction: make isolate_lru_page() filter-aware again Mel Gorman
2011-12-16 3:34 ` Rik van Riel
2011-12-18 1:53 ` Minchan Kim
2011-12-14 15:41 ` [PATCH 07/11] mm: page allocator: Do not call direct reclaim for THP allocations while compaction is deferred Mel Gorman
2011-12-16 4:10 ` Rik van Riel
2011-12-14 15:41 ` [PATCH 08/11] mm: compaction: Introduce sync-light migration for use by compaction Mel Gorman
2011-12-16 4:31 ` Rik van Riel
2011-12-18 2:05 ` Minchan Kim
2011-12-19 11:45 ` Mel Gorman
2011-12-20 7:18 ` Minchan Kim
2012-01-13 21:25 ` Andrew Morton
2012-01-16 11:33 ` Mel Gorman
2011-12-14 15:41 ` [PATCH 09/11] mm: vmscan: When reclaiming for compaction, ensure there are sufficient free pages available Mel Gorman
2011-12-16 4:35 ` Rik van Riel
2011-12-14 15:41 ` [PATCH 10/11] mm: vmscan: Check if reclaim should really abort even if compaction_ready() is true for one zone Mel Gorman
2011-12-16 4:38 ` Rik van Riel
2011-12-16 11:29 ` Mel Gorman
2011-12-14 15:41 ` [PATCH 11/11] mm: Isolate pages for immediate reclaim on their own LRU Mel Gorman
2011-12-16 4:47 ` Rik van Riel
2011-12-16 12:26 ` Mel Gorman
2011-12-16 15:17 ` Johannes Weiner
2011-12-16 16:07 ` Mel Gorman
2011-12-19 16:14 ` Johannes Weiner
2011-12-17 16:08 ` Minchan Kim
2011-12-19 13:26 ` Mel Gorman
2011-12-20 7:10 ` Minchan Kim
2011-12-20 9:55 ` Mel Gorman [this message]
2011-12-23 19:08 ` Hugh Dickins
2011-12-29 16:59 ` Mel Gorman
2011-12-29 19:31 ` Rik van Riel
2011-12-30 11:27 ` Mel Gorman
2011-12-16 22:56 ` [PATCH 0/11] Reduce compaction-related stalls and improve asynchronous migration of dirty pages v6 Andrew Morton
2011-12-19 14:40 ` Mel Gorman
2011-12-16 23:37 ` Andrew Morton
2011-12-19 14:20 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2011-12-01 17:36 [PATCH 0/11] Reduce compaction-related stalls and improve asynchronous migration of dirty pages v5 Mel Gorman
2011-12-01 17:36 ` [PATCH 11/11] mm: Isolate pages for immediate reclaim on their own LRU Mel Gorman
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