The patch titled
Subject: mm, compaction: reduce unnecessary skipping of migration target scanner
has been added to the -mm tree. Its filename is
mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, compaction: reduce unnecessary skipping of migration target scanner
The fast isolation of pages can move the scanner faster than is necessary
depending on the contents of the free list. This patch will only allow
the fast isolation to initialise the scanner and advance it slowly. The
primary means of moving the scanner forward is via the linear scanner to
reduce the likelihood the migration source/target scanners meet
prematurely triggering a rescan.
4.20.0 4.20.0
noresched-v2r15 slowfree-v2r15
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 2736.50 ( 0.00%) 2512.53 ( 8.18%)
Amean fault-both-5 4133.70 ( 0.00%) 4159.43 ( -0.62%)
Amean fault-both-7 5738.61 ( 0.00%) 5950.15 ( -3.69%)
Amean fault-both-12 9392.82 ( 0.00%) 8674.38 ( 7.65%)
Amean fault-both-18 13257.15 ( 0.00%) 12850.79 ( 3.07%)
Amean fault-both-24 16859.44 ( 0.00%) 17242.86 ( -2.27%)
Amean fault-both-30 16249.30 ( 0.00%) 19404.18 * -19.42%*
Amean fault-both-32 14904.71 ( 0.00%) 16200.79 ( -8.70%)
The impact to latency, success rates and scan rates is marginal but
avoiding unnecessary restarts is important. It helps later patches that
are more careful about how pageblocks are treated as earlier iterations of
those patches hit corner cases where the restarts were punishing and very
visible.
Link: http://lkml.kernel.org/r/20190104125011.16071-21-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/compaction.c~mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner
+++ a/mm/compaction.c
@@ -324,10 +324,9 @@ static void update_cached_migrate(struct
* future. The information is later cleared by __reset_isolation_suitable().
*/
static void update_pageblock_skip(struct compact_control *cc,
- struct page *page, unsigned long nr_isolated)
+ struct page *page, unsigned long pfn)
{
struct zone *zone = cc->zone;
- unsigned long pfn;
if (cc->no_set_skip_hint)
return;
@@ -335,13 +334,8 @@ static void update_pageblock_skip(struct
if (!page)
return;
- if (nr_isolated)
- return;
-
set_pageblock_skip(page);
- pfn = page_to_pfn(page);
-
/* Update where async and sync compaction should restart */
if (pfn < zone->compact_cached_free_pfn)
zone->compact_cached_free_pfn = pfn;
@@ -359,7 +353,7 @@ static inline bool pageblock_skip_persis
}
static inline void update_pageblock_skip(struct compact_control *cc,
- struct page *page, unsigned long nr_isolated)
+ struct page *page, unsigned long pfn)
{
}
@@ -450,7 +444,7 @@ static unsigned long isolate_freepages_b
bool strict)
{
int nr_scanned = 0, total_isolated = 0;
- struct page *cursor, *valid_page = NULL;
+ struct page *cursor;
unsigned long flags = 0;
bool locked = false;
unsigned long blockpfn = *start_pfn;
@@ -477,9 +471,6 @@ static unsigned long isolate_freepages_b
if (!pfn_valid_within(blockpfn))
goto isolate_fail;
- if (!valid_page)
- valid_page = page;
-
/*
* For compound pages such as THP and hugetlbfs, we can save
* potentially a lot of iterations if we skip them at once.
@@ -576,10 +567,6 @@ isolate_fail:
if (strict && blockpfn < end_pfn)
total_isolated = 0;
- /* Update the pageblock-skip if the whole pageblock was scanned */
- if (blockpfn == end_pfn)
- update_pageblock_skip(cc, valid_page, total_isolated);
-
cc->total_free_scanned += nr_scanned;
if (total_isolated)
count_compact_events(COMPACTISOLATED, total_isolated);
@@ -1295,8 +1282,10 @@ fast_isolate_freepages(struct compact_co
}
}
- if (highest && highest > cc->zone->compact_cached_free_pfn)
+ if (highest && highest >= cc->zone->compact_cached_free_pfn) {
+ highest -= pageblock_nr_pages;
cc->zone->compact_cached_free_pfn = highest;
+ }
cc->total_free_scanned += nr_scanned;
if (!page)
@@ -1376,6 +1365,10 @@ static void isolate_freepages(struct com
isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn,
freelist, false);
+ /* Update the skip hint if the full pageblock was scanned */
+ if (isolate_start_pfn == block_end_pfn)
+ update_pageblock_skip(cc, page, block_start_pfn);
+
/* Are enough freepages isolated? */
if (cc->nr_freepages >= cc->nr_migratepages) {
if (isolate_start_pfn >= block_end_pfn) {
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-do-not-wake-kswapd-with-zone-lock-held.patch
mm-compaction-shrink-compact_control.patch
mm-compaction-rearrange-compact_control.patch
mm-compaction-remove-last_migrated_pfn-from-compact_control.patch
mm-compaction-remove-unnecessary-zone-parameter-in-some-instances.patch
mm-compaction-rename-map_pages-to-split_map_pages.patch
mm-compaction-skip-pageblocks-with-reserved-pages.patch
mm-migrate-immediately-fail-migration-of-a-page-with-no-migration-handler.patch
mm-compaction-always-finish-scanning-of-a-full-pageblock.patch
mm-compaction-use-the-page-allocator-bulk-free-helper-for-lists-of-pages.patch
mm-compaction-ignore-the-fragmentation-avoidance-boost-for-isolation-and-compaction.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-source.patch
mm-compaction-keep-migration-source-private-to-a-single-compaction-instance.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-target.patch
mm-compaction-avoid-rescanning-the-same-pageblock-multiple-times.patch
mm-compaction-finish-pageblock-scanning-on-contention.patch
mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
mm-compaction-rework-compact_should_abort-as-compact_check_resched.patch
mm-compaction-do-not-consider-a-need-to-reschedule-as-contention.patch
mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner.patch
mm-compaction-round-robin-the-order-while-searching-the-free-lists-for-a-target.patch
mm-compaction-sample-pageblocks-for-free-pages.patch
mm-compaction-be-selective-about-what-pageblocks-to-clear-skip-hints.patch
mm-compaction-capture-a-page-under-direct-compaction.patch
mm-compaction-do-not-direct-compact-remote-memory.patch
