From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>, Linux-MM <linux-mm@kvack.org>
Cc: David Rientjes <rientjes@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
ying.huang@intel.com, kirill@shutemov.name,
Andrew Morton <akpm@linux-foundation.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 20/25] mm, compaction: Reduce unnecessary skipping of migration target scanner
Date: Thu, 17 Jan 2019 18:58:30 +0100 [thread overview]
Message-ID: <8e310c2a-5f2e-ee99-24c5-10a71972699a@suse.cz> (raw)
In-Reply-To: <20190104125011.16071-21-mgorman@techsingularity.net>
On 1/4/19 1:50 PM, Mel Gorman wrote:
> 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.
Maybe I've seen enough code today and need to stop, but AFAICS the description
here doesn't match the actual code changes? What I see are some cleanups, and a
change in free scanner that will set pageblock skip bit after a pageblock has
been scanned, even if there were pages isolated, while previously it would set
the skip bit only if nothing was isolated.
> 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.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> mm/compaction.c | 27 ++++++++++-----------------
> 1 file changed, 10 insertions(+), 17 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 75eb0d40d4d7..6c5552c6d8f9 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -324,10 +324,9 @@ static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
> * 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 compact_control *cc,
> 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_persistent(struct page *page)
> }
>
> 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_block(struct compact_control *cc,
> 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_block(struct compact_control *cc,
> 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 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
> 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_control *cc)
> }
> }
>
> - 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 compact_control *cc)
> 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) {
>
next prev parent reply other threads:[~2019-01-17 17:58 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 12:49 [PATCH 00/25] Increase success rates and reduce latency of compaction v2 Mel Gorman
2019-01-04 12:49 ` [PATCH 01/25] mm, compaction: Shrink compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 02/25] mm, compaction: Rearrange compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 03/25] mm, compaction: Remove last_migrated_pfn from compact_control Mel Gorman
2019-01-04 12:49 ` [PATCH 04/25] mm, compaction: Remove unnecessary zone parameter in some instances Mel Gorman
2019-01-15 11:43 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 05/25] mm, compaction: Rename map_pages to split_map_pages Mel Gorman
2019-01-15 11:59 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 06/25] mm, compaction: Skip pageblocks with reserved pages Mel Gorman
2019-01-15 12:10 ` Vlastimil Babka
2019-01-15 12:50 ` Mel Gorman
2019-01-16 9:42 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 07/25] mm, migrate: Immediately fail migration of a page with no migration handler Mel Gorman
2019-01-04 12:49 ` [PATCH 08/25] mm, compaction: Always finish scanning of a full pageblock Mel Gorman
2019-01-04 12:49 ` [PATCH 09/25] mm, compaction: Use the page allocator bulk-free helper for lists of pages Mel Gorman
2019-01-15 12:39 ` Vlastimil Babka
2019-01-16 9:46 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 10/25] mm, compaction: Ignore the fragmentation avoidance boost for isolation and compaction Mel Gorman
2019-01-15 13:18 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 11/25] mm, compaction: Use free lists to quickly locate a migration source Mel Gorman
2019-01-16 13:15 ` Vlastimil Babka
2019-01-16 14:33 ` Mel Gorman
2019-01-16 15:00 ` Vlastimil Babka
2019-01-16 15:43 ` Mel Gorman
2019-01-04 12:49 ` [PATCH 12/25] mm, compaction: Keep migration source private to a single compaction instance Mel Gorman
2019-01-16 15:45 ` Vlastimil Babka
2019-01-16 16:15 ` Mel Gorman
2019-01-17 9:29 ` Vlastimil Babka
2019-01-17 9:40 ` Vlastimil Babka
2019-01-04 12:49 ` [PATCH 13/25] mm, compaction: Use free lists to quickly locate a migration target Mel Gorman
2019-01-17 14:36 ` Vlastimil Babka
2019-01-17 15:51 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 14/25] mm, compaction: Avoid rescanning the same pageblock multiple times Mel Gorman
2019-01-17 15:16 ` Vlastimil Babka
2019-01-17 16:00 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 15/25] mm, compaction: Finish pageblock scanning on contention Mel Gorman
2019-01-17 16:38 ` Vlastimil Babka
2019-01-17 17:11 ` Mel Gorman
2019-01-18 8:57 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 16/25] mm, compaction: Check early for huge pages encountered by the migration scanner Mel Gorman
2019-01-17 17:01 ` Vlastimil Babka
2019-01-17 17:35 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 17/25] mm, compaction: Keep cached migration PFNs synced for unusable pageblocks Mel Gorman
2019-01-17 17:17 ` Vlastimil Babka
2019-01-17 17:37 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 18/25] mm, compaction: Rework compact_should_abort as compact_check_resched Mel Gorman
2019-01-17 17:27 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 19/25] mm, compaction: Do not consider a need to reschedule as contention Mel Gorman
2019-01-17 17:33 ` Vlastimil Babka
2019-01-17 18:05 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 20/25] mm, compaction: Reduce unnecessary skipping of migration target scanner Mel Gorman
2019-01-17 17:58 ` Vlastimil Babka [this message]
2019-01-17 19:39 ` Mel Gorman
2019-01-18 9:09 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 21/25] mm, compaction: Round-robin the order while searching the free lists for a target Mel Gorman
2019-01-18 9:17 ` Vlastimil Babka
2019-01-04 12:50 ` [PATCH 22/25] mm, compaction: Sample pageblocks for free pages Mel Gorman
2019-01-18 10:38 ` Vlastimil Babka
2019-01-18 13:44 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 23/25] mm, compaction: Be selective about what pageblocks to clear skip hints Mel Gorman
2019-01-18 12:55 ` Vlastimil Babka
2019-01-18 14:10 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 24/25] mm, compaction: Capture a page under direct compaction Mel Gorman
2019-01-18 13:40 ` Vlastimil Babka
2019-01-18 14:39 ` Mel Gorman
2019-01-04 12:50 ` [PATCH 25/25] mm, compaction: Do not direct compact remote memory Mel Gorman
2019-01-18 13:51 ` Vlastimil Babka
2019-01-18 14:46 ` Mel Gorman
2019-01-07 23:43 ` [PATCH 00/25] Increase success rates and reduce latency of compaction v2 Andrew Morton
2019-01-08 9:12 ` Mel Gorman
2019-01-09 11:13 ` [PATCH] mm, compaction: Use free lists to quickly locate a migration target -fix Mel Gorman
2019-01-09 19:27 ` Andrew Morton
2019-01-09 21:26 ` Mel Gorman
2019-01-09 11:15 ` [PATCH] mm, compaction: Finish pageblock scanning on contention -fix Mel Gorman
2019-01-09 11:16 ` [PATCH] mm, compaction: Round-robin the order while searching the free lists for a target -fix Mel Gorman
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