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Date: Mon, 29 Sep 2014 16:50:38 +0900
From: Joonsoo Kim <iamjoonsoo.kim@....com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Minchan Kim <minchan@...nel.org>,
Michal Nazarewicz <mina86@...a86.com>,
Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Christoph Lameter <cl@...ux.com>,
Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v6 05/13] mm, compaction: move pageblock checks up from
isolate_migratepages_range()
On Mon, Aug 04, 2014 at 10:55:16AM +0200, Vlastimil Babka wrote:
> isolate_migratepages_range() is the main function of the compaction scanner,
> called either on a single pageblock by isolate_migratepages() during regular
> compaction, or on an arbitrary range by CMA's __alloc_contig_migrate_range().
> It currently perfoms two pageblock-wide compaction suitability checks, and
> because of the CMA callpath, it tracks if it crossed a pageblock boundary in
> order to repeat those checks.
>
> However, closer inspection shows that those checks are always true for CMA:
> - isolation_suitable() is true because CMA sets cc->ignore_skip_hint to true
> - migrate_async_suitable() check is skipped because CMA uses sync compaction
>
> We can therefore move the compaction-specific checks to isolate_migratepages()
> and simplify isolate_migratepages_range(). Furthermore, we can mimic the
> freepage scanner family of functions, which has isolate_freepages_block()
> function called both by compaction from isolate_freepages() and by CMA from
> isolate_freepages_range(), where each use-case adds own specific glue code.
> This allows further code simplification.
>
> Thus, we rename isolate_migratepages_range() to isolate_migratepages_block()
> and limit its functionality to a single pageblock (or its subset). For CMA,
> a new different isolate_migratepages_range() is created as a CMA-specific
> wrapper for the _block() function. The checks specific to compaction are moved
> to isolate_migratepages(). As part of the unification of these two families of
> functions, we remove the redundant zone parameter where applicable, since zone
> pointer is already passed in cc->zone.
>
> Furthermore, going back to compact_zone() and compact_finished() when pageblock
> is found unsuitable (now by isolate_migratepages()) is wasteful - the checks
> are meant to skip pageblocks quickly. The patch therefore also introduces a
> simple loop into isolate_migratepages() so that it does not return immediately
> on failed pageblock checks, but keeps going until isolate_migratepages_range()
> gets called once. Similarily to isolate_freepages(), the function periodically
> checks if it needs to reschedule or abort async compaction.
>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Cc: Minchan Kim <minchan@...nel.org>
> Acked-by: Mel Gorman <mgorman@...e.de>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Michal Nazarewicz <mina86@...a86.com>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: David Rientjes <rientjes@...gle.com>
> ---
> mm/compaction.c | 235 +++++++++++++++++++++++++++++++++-----------------------
> mm/internal.h | 4 +-
> mm/page_alloc.c | 3 +-
> 3 files changed, 141 insertions(+), 101 deletions(-)
>
Hello,
This patch needs one fix.
Please see below.
Thanks.
---------->8-------------
>From 3ba15d35c00e0d913d603d2972678bf74554ed60 Mon Sep 17 00:00:00 2001
From: Joonsoo Kim <iamjoonsoo.kim@....com>
Date: Mon, 29 Sep 2014 15:08:07 +0900
Subject: [PATCH] mm/compaction: fix isolated page counting bug in compaction
acct_isolated() is the function to adjust isolated page count. It
iterates cc->migratepages list and add
NR_ISOLATED_ANON/NR_ISOLATED_FILE count according to number of anon,
file pages in migratepages list, respectively. Before commit (mm,
compaction: move pageblock checks up from isolate_migratepages_range()),
it is called just once in isolate_migratepages_range(), but, after commit,
it is called in newly introduced isolate_migratepages_block() and this
isolate_migratepages_block() could be called many times in
isolate_migratepages_range() so that some page could be counted more
than once. This duplicate counting bug results in hang in cma_alloc(),
because too_many_isolated() returns true continually.
This patch fixes this bug by moving acct_isolated() into upper layer
function, isolate_migratepages_range() and isolate_migratepages().
After this change, isolated page would be counted only once so
problem would be gone.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
mm/compaction.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 7d9d92e..48129b6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -514,22 +514,19 @@ isolate_freepages_range(struct compact_control *cc,
}
/* Update the number of anon and file isolated pages in the zone */
-static void acct_isolated(struct zone *zone, bool locked, struct compact_control *cc)
+static void acct_isolated(struct zone *zone, struct compact_control *cc)
{
struct page *page;
unsigned int count[2] = { 0, };
+ if (list_empty(&cc->migratepages))
+ return;
+
list_for_each_entry(page, &cc->migratepages, lru)
count[!!page_is_file_cache(page)]++;
- /* If locked we can use the interrupt unsafe versions */
- if (locked) {
- __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
- __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
- } else {
- mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
- mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
- }
+ mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]);
+ mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);
}
/* Similar to reclaim, but different enough that they don't share logic */
@@ -726,8 +723,6 @@ isolate_success:
if (unlikely(low_pfn > end_pfn))
low_pfn = end_pfn;
- acct_isolated(zone, locked, cc);
-
if (locked)
spin_unlock_irqrestore(&zone->lru_lock, flags);
@@ -789,6 +784,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
break;
}
}
+ acct_isolated(cc->zone, cc);
return pfn;
}
@@ -1028,6 +1024,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
break;
}
+ acct_isolated(zone, cc);
/* Record where migration scanner will be restarted */
cc->migrate_pfn = low_pfn;
--
1.7.9.5
--
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