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From: Alexander Duyck <alexander.duyck@gmail.com>
To: alex.shi@linux.alibaba.com
Cc: yang.shi@linux.alibaba.com, lkp@intel.com, rong.a.chen@intel.com,
	khlebnikov@yandex-team.ru, kirill@shutemov.name,
	hughd@google.com, linux-kernel@vger.kernel.org,
	alexander.duyck@gmail.com, daniel.m.jordan@oracle.com,
	linux-mm@kvack.org, shakeelb@google.com, willy@infradead.org,
	hannes@cmpxchg.org, tj@kernel.org, cgroups@vger.kernel.org,
	akpm@linux-foundation.org, richard.weiyang@gmail.com,
	mgorman@techsingularity.net, iamjoonsoo.kim@lge.com
Subject: [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip
Date: Wed, 12 Aug 2020 21:02:32 -0700
Message-ID: <20200813040232.13054.82417.stgit@localhost.localdomain> (raw)
In-Reply-To: <20200813035100.13054.25671.stgit@localhost.localdomain>

From: Alexander Duyck <alexander.h.duyck@linux.intel.com>

The only user of test_and_set_skip was isolate_migratepages_block and it
was using it after a call that was testing and clearing the LRU flag. As
such it really didn't need to be behind the LRU lock anymore as it wasn't
really fulfilling its purpose.

With that being the case we can simply drop the bit and instead directly
just call the set_pageblock_skip function if the page we are working on is
the valid_page at the start of the pageblock. It shouldn't be possible for
us to encounter the bit being set since we obtained the LRU flag for the
first page in the pageblock which means we would have exclusive access to
setting the skip bit. As such we don't need to worry about the abort case
since no other thread will be able to call what used to be
test_and_set_skip.

Since we have dropped the late abort case we can drop the code that was
clearing the LRU flag and calling page_put since the abort case will now
not be holding a reference to a page.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 mm/compaction.c |   50 +++++++-------------------------------------------
 1 file changed, 7 insertions(+), 43 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 5021a18ef722..c1e9918f9dd4 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -399,29 +399,6 @@ void reset_isolation_suitable(pg_data_t *pgdat)
 	}
 }
 
-/*
- * Sets the pageblock skip bit if it was clear. Note that this is a hint as
- * locks are not required for read/writers. Returns true if it was already set.
- */
-static bool test_and_set_skip(struct compact_control *cc, struct page *page,
-							unsigned long pfn)
-{
-	bool skip;
-
-	/* Do no update if skip hint is being ignored */
-	if (cc->ignore_skip_hint)
-		return false;
-
-	if (!IS_ALIGNED(pfn, pageblock_nr_pages))
-		return false;
-
-	skip = get_pageblock_skip(page);
-	if (!skip && !cc->no_set_skip_hint)
-		skip = !set_pageblock_skip(page);
-
-	return skip;
-}
-
 static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
 {
 	struct zone *zone = cc->zone;
@@ -480,12 +457,6 @@ static inline void update_pageblock_skip(struct compact_control *cc,
 static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
 {
 }
-
-static bool test_and_set_skip(struct compact_control *cc, struct page *page,
-							unsigned long pfn)
-{
-	return false;
-}
 #endif /* CONFIG_COMPACTION */
 
 /*
@@ -895,7 +866,6 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
 			if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
 				low_pfn = end_pfn;
-				page = NULL;
 				goto isolate_abort;
 			}
 			valid_page = page;
@@ -991,6 +961,13 @@ static bool too_many_isolated(pg_data_t *pgdat)
 		if (!TestClearPageLRU(page))
 			goto isolate_fail_put;
 
+		/* Indicate that we want exclusive access to this pageblock */
+		if (page == valid_page) {
+			skip_updated = true;
+			if (!cc->ignore_skip_hint)
+				set_pageblock_skip(page);
+		}
+
 		/* If we already hold the lock, we can skip some rechecking */
 		if (!lruvec || !lruvec_holds_page_lru_lock(page, lruvec)) {
 			if (lruvec)
@@ -1002,13 +979,6 @@ static bool too_many_isolated(pg_data_t *pgdat)
 
 			lruvec_memcg_debug(lruvec, page);
 
-			/* Try get exclusive access under lock */
-			if (!skip_updated) {
-				skip_updated = true;
-				if (test_and_set_skip(cc, page, low_pfn))
-					goto isolate_abort;
-			}
-
 			/*
 			 * Page become compound since the non-locked check,
 			 * and it's on LRU. It can only be a THP so the order
@@ -1094,15 +1064,9 @@ static bool too_many_isolated(pg_data_t *pgdat)
 	if (unlikely(low_pfn > end_pfn))
 		low_pfn = end_pfn;
 
-	page = NULL;
-
 isolate_abort:
 	if (lruvec)
 		unlock_page_lruvec_irqrestore(lruvec, flags);
-	if (page) {
-		SetPageLRU(page);
-		put_page(page);
-	}
 
 	/*
 	 * Updated the cached scanner pfn once the pageblock has been scanned



  parent reply index

Thread overview: 102+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25 12:59 [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-25 12:59 ` [PATCH v17 01/21] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-08-06  3:47   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 02/21] mm/page_idle: no unlikely double check for idle page counting Alex Shi
2020-07-25 12:59 ` [PATCH v17 03/21] mm/compaction: correct the comments of compact_defer_shift Alex Shi
2020-07-27 17:29   ` Alexander Duyck
2020-07-28 11:59     ` Alex Shi
2020-07-28 14:17       ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 04/21] mm/compaction: rename compact_deferred as compact_should_defer Alex Shi
2020-07-25 12:59 ` [PATCH v17 05/21] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi
2020-07-25 12:59 ` [PATCH v17 06/21] mm/thp: clean up lru_add_page_tail Alex Shi
2020-07-25 12:59 ` [PATCH v17 07/21] mm/thp: remove code path which never got into Alex Shi
2020-07-25 12:59 ` [PATCH v17 08/21] mm/thp: narrow lru locking Alex Shi
2020-07-25 12:59 ` [PATCH v17 09/21] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2020-07-25 12:59 ` [PATCH v17 10/21] mm/swap: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 11/21] mm/lru: move lru_lock holding in func lru_note_cost_page Alex Shi
2020-08-05 21:18   ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 12/21] mm/lru: move lock into lru_note_cost Alex Shi
2020-07-25 12:59 ` [PATCH v17 13/21] mm/lru: introduce TestClearPageLRU Alex Shi
2020-07-29  3:53   ` Alex Shi
2020-08-05 22:43     ` Alexander Duyck
2020-08-06  1:54       ` Alex Shi
2020-08-06 14:41         ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alex Shi
2020-08-04 21:35   ` Alexander Duyck
2020-08-06 18:38   ` Alexander Duyck
2020-08-07  3:24     ` Alex Shi
2020-08-07 14:51       ` Alexander Duyck
2020-08-10 13:10         ` Alex Shi
2020-08-10 14:41           ` Alexander Duyck
2020-08-11  8:22             ` Alex Shi
2020-08-11 14:47               ` Alexander Duyck
2020-08-12 11:43                 ` Alex Shi
2020-08-12 12:16                   ` Alex Shi
2020-08-12 16:51                   ` Alexander Duyck
2020-08-13  1:46                     ` Alex Shi
2020-08-13  2:17                       ` Alexander Duyck
2020-08-13  3:52                         ` Alex Shi
2020-08-13  4:02                       ` [RFC PATCH 0/3] " Alexander Duyck
2020-08-13  4:02                         ` [RFC PATCH 1/3] mm: Drop locked from isolate_migratepages_block Alexander Duyck
2020-08-13  6:56                           ` Alex Shi
2020-08-13 14:32                             ` Alexander Duyck
2020-08-14  7:25                               ` Alex Shi
2020-08-13  7:44                           ` Alex Shi
2020-08-13 14:26                             ` Alexander Duyck
2020-08-13  4:02                         ` Alexander Duyck [this message]
2020-08-14  7:19                           ` [RFC PATCH 2/3] mm: Drop use of test_and_set_skip in favor of just setting skip Alex Shi
2020-08-14 14:24                             ` Alexander Duyck
2020-08-14 21:15                               ` Alexander Duyck
2020-08-15  9:49                                 ` Alex Shi
2020-08-17 15:38                                   ` Alexander Duyck
2020-08-18  6:50                           ` Alex Shi
2020-08-13  4:02                         ` [RFC PATCH 3/3] mm: Identify compound pages sooner in isolate_migratepages_block Alexander Duyck
2020-08-14  7:20                           ` Alex Shi
2020-08-17 22:58   ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page() Alex Shi
2020-07-25 12:59 ` [PATCH v17 16/21] mm/swap: serialize memcg changes in pagevec_lru_move_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 17/21] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-07-27 23:34   ` Alexander Duyck
2020-07-28  7:15     ` Alex Shi
2020-07-28 11:19     ` Alex Shi
2020-07-28 14:54       ` Alexander Duyck
2020-07-29  1:00         ` Alex Shi
2020-07-29  1:27           ` Alexander Duyck
2020-07-29  2:27             ` Alex Shi
2020-07-28 15:39     ` Alex Shi
2020-07-28 15:55       ` Alexander Duyck
2020-07-29  0:48         ` Alex Shi
2020-07-29  3:54   ` Alex Shi
2020-08-06  7:41   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 18/21] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-07-29 17:52   ` Alexander Duyck
2020-07-30  6:08     ` Alex Shi
2020-07-31 14:20       ` Alexander Duyck
2020-07-31 21:14   ` [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid alexander.h.duyck
2020-07-31 23:54     ` Alex Shi
2020-08-02 18:20       ` Alexander Duyck
2020-08-04  6:13         ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 19/21] mm/vmscan: use relock for move_pages_to_lru Alex Shi
2020-08-03 22:49   ` Alexander Duyck
2020-08-04  6:23     ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 20/21] mm/pgdat: remove pgdat lru_lock Alex Shi
2020-08-03 22:42   ` Alexander Duyck
2020-08-03 22:45     ` Alexander Duyck
2020-08-04  6:22       ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 21/21] mm/lru: revise the comments of lru_lock Alex Shi
2020-08-03 22:37   ` Alexander Duyck
2020-08-04 10:04     ` Alex Shi
2020-08-04 14:29       ` Alexander Duyck
2020-08-06  1:39         ` Alex Shi
2020-08-06 16:27           ` Alexander Duyck
2020-07-27  5:40 ` [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-29 14:49   ` Alex Shi
2020-07-29 18:06     ` Hugh Dickins
2020-07-30  2:16       ` Alex Shi
2020-08-03 15:07         ` Michal Hocko
2020-08-04  6:14           ` Alex Shi
2020-07-31 21:31 ` Alexander Duyck
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:37 ` Alex Shi
2020-08-04  8:37 ` Alex Shi

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