From: Vlastimil Babka <vbabka@suse.cz> To: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman <mgorman@techsingularity.net>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz> Subject: [PATCH 1/3] mm, compaction: extend pageblock_skip_persistent() to all compound pages Date: Thu, 2 Nov 2017 13:17:04 +0100 [thread overview] Message-ID: <20171102121706.21504-1-vbabka@suse.cz> (raw) The pageblock_skip_persistent() function checks for HugeTLB pages of pageblock order. When clearing pageblock skip bits for compaction, the bits are not cleared for such pageblocks, because they cannot contain base pages suitable for migration, nor free pages to use as migration targets. This optimization can be simply extended to all compound pages of order equal or larger than pageblock order, because migrating such pages (if they support it) cannot help sub-pageblock fragmentation. This includes THP's and also gigantic HugeTLB pages, which the current implementation doesn't persistently skip due to a strict pageblock_order equality check and not recognizing tail pages. While THP pages are generally less "persistent" than HugeTLB, we can still expect that if a THP exists at the point of __reset_isolation_suitable(), it will exist also during the subsequent compaction run. The time difference here could be actually smaller than between a compaction run that sets a (non-persistent) skip bit on a THP, and the next compaction run that observes it. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- mm/compaction.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 445490ab2603..be7ab160f251 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -218,17 +218,21 @@ static void reset_cached_positions(struct zone *zone) } /* - * Hugetlbfs pages should consistenly be skipped until updated by the hugetlb - * subsystem. It is always pointless to compact pages of pageblock_order and - * the free scanner can reconsider when no longer huge. + * Compound pages of >= pageblock_order should consistenly be skipped until + * released. It is always pointless to compact pages of such order (if they are + * migratable), and the pageblocks they occupy cannot contain any free pages. */ -static bool pageblock_skip_persistent(struct page *page, unsigned int order) +static bool pageblock_skip_persistent(struct page *page) { - if (!PageHuge(page)) + if (!PageCompound(page)) return false; - if (order != pageblock_order) - return false; - return true; + + page = compound_head(page); + + if (compound_order(page) >= pageblock_order) + return true; + + return false; } /* @@ -255,7 +259,7 @@ static void __reset_isolation_suitable(struct zone *zone) continue; if (zone != page_zone(page)) continue; - if (pageblock_skip_persistent(page, compound_order(page))) + if (pageblock_skip_persistent(page)) continue; clear_pageblock_skip(page); @@ -322,8 +326,7 @@ static inline bool isolation_suitable(struct compact_control *cc, return true; } -static inline bool pageblock_skip_persistent(struct page *page, - unsigned int order) +static inline bool pageblock_skip_persistent(struct page *page) { return false; } -- 2.14.3
WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka@suse.cz> To: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman <mgorman@techsingularity.net>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Vlastimil Babka <vbabka@suse.cz> Subject: [PATCH 1/3] mm, compaction: extend pageblock_skip_persistent() to all compound pages Date: Thu, 2 Nov 2017 13:17:04 +0100 [thread overview] Message-ID: <20171102121706.21504-1-vbabka@suse.cz> (raw) The pageblock_skip_persistent() function checks for HugeTLB pages of pageblock order. When clearing pageblock skip bits for compaction, the bits are not cleared for such pageblocks, because they cannot contain base pages suitable for migration, nor free pages to use as migration targets. This optimization can be simply extended to all compound pages of order equal or larger than pageblock order, because migrating such pages (if they support it) cannot help sub-pageblock fragmentation. This includes THP's and also gigantic HugeTLB pages, which the current implementation doesn't persistently skip due to a strict pageblock_order equality check and not recognizing tail pages. While THP pages are generally less "persistent" than HugeTLB, we can still expect that if a THP exists at the point of __reset_isolation_suitable(), it will exist also during the subsequent compaction run. The time difference here could be actually smaller than between a compaction run that sets a (non-persistent) skip bit on a THP, and the next compaction run that observes it. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> --- mm/compaction.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 445490ab2603..be7ab160f251 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -218,17 +218,21 @@ static void reset_cached_positions(struct zone *zone) } /* - * Hugetlbfs pages should consistenly be skipped until updated by the hugetlb - * subsystem. It is always pointless to compact pages of pageblock_order and - * the free scanner can reconsider when no longer huge. + * Compound pages of >= pageblock_order should consistenly be skipped until + * released. It is always pointless to compact pages of such order (if they are + * migratable), and the pageblocks they occupy cannot contain any free pages. */ -static bool pageblock_skip_persistent(struct page *page, unsigned int order) +static bool pageblock_skip_persistent(struct page *page) { - if (!PageHuge(page)) + if (!PageCompound(page)) return false; - if (order != pageblock_order) - return false; - return true; + + page = compound_head(page); + + if (compound_order(page) >= pageblock_order) + return true; + + return false; } /* @@ -255,7 +259,7 @@ static void __reset_isolation_suitable(struct zone *zone) continue; if (zone != page_zone(page)) continue; - if (pageblock_skip_persistent(page, compound_order(page))) + if (pageblock_skip_persistent(page)) continue; clear_pageblock_skip(page); @@ -322,8 +326,7 @@ static inline bool isolation_suitable(struct compact_control *cc, return true; } -static inline bool pageblock_skip_persistent(struct page *page, - unsigned int order) +static inline bool pageblock_skip_persistent(struct page *page) { return false; } -- 2.14.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next reply other threads:[~2017-11-02 12:17 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-11-02 12:17 Vlastimil Babka [this message] 2017-11-02 12:17 ` [PATCH 1/3] mm, compaction: extend pageblock_skip_persistent() to all compound pages Vlastimil Babka 2017-11-02 12:17 ` [PATCH 2/3] mm, compaction: split off flag for not updating skip hints Vlastimil Babka 2017-11-02 12:17 ` Vlastimil Babka 2017-11-02 13:09 ` Mel Gorman 2017-11-02 13:09 ` Mel Gorman 2017-11-02 12:17 ` [PATCH 3/3] mm, compaction: remove unneeded pageblock_skip_persistent() checks Vlastimil Babka 2017-11-02 12:17 ` Vlastimil Babka 2017-11-02 13:04 ` [PATCH 1/3] mm, compaction: extend pageblock_skip_persistent() to all compound pages Mel Gorman 2017-11-02 13:04 ` Mel Gorman 2017-11-03 20:37 ` David Rientjes 2017-11-03 20:37 ` David Rientjes
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