The patch titled
Subject: mm/page_alloc: simplify locking during free_unref_page_list
has been added to the -mm mm-unstable branch. Its filename is
mm-page_alloc-simplify-locking-during-free_unref_page_list.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-simplify-locking-during-free_unref_page_list.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm/page_alloc: simplify locking during free_unref_page_list
Date: Tue, 22 Nov 2022 13:12:29 +0000
While freeing a large list, the zone lock will be released and reacquired
to avoid long hold times since commit c24ad77d962c ("mm/page_alloc.c:
avoid excessive IRQ disabled times in free_unref_page_list()"). As
suggested by Vlastimil Babka, the lockrelease/reacquire logic can be
simplified by reusing the logic that acquires a different lock when
changing zones.
Link: https://lkml.kernel.org/r/20221122131229.5263-3-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 25 +++++++++----------------
1 file changed, 9 insertions(+), 16 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-simplify-locking-during-free_unref_page_list
+++ a/mm/page_alloc.c
@@ -3540,13 +3540,19 @@ void free_unref_page_list(struct list_he
list_del(&page->lru);
migratetype = get_pcppage_migratetype(page);
- /* Different zone, different pcp lock. */
- if (zone != locked_zone) {
+ /*
+ * Either different zone requiring a different pcp lock or
+ * excessive lock hold times when freeing a large list of
+ * pages.
+ */
+ if (zone != locked_zone || batch_count == SWAP_CLUSTER_MAX) {
if (pcp) {
pcp_spin_unlock(pcp);
pcp_trylock_finish(UP_flags);
}
+ batch_count = 0;
+
/*
* trylock is necessary as pages may be getting freed
* from IRQ or SoftIRQ context after an IO completion.
@@ -3561,7 +3567,6 @@ void free_unref_page_list(struct list_he
continue;
}
locked_zone = zone;
- batch_count = 0;
}
/*
@@ -3573,19 +3578,7 @@ void free_unref_page_list(struct list_he
trace_mm_page_free_batched(page);
free_unref_page_commit(zone, pcp, page, migratetype, 0);
-
- /*
- * Guard against excessive lock hold times when freeing
- * a large list of pages. Lock will be reacquired if
- * necessary on the next iteration.
- */
- if (++batch_count == SWAP_CLUSTER_MAX) {
- pcp_spin_unlock(pcp);
- pcp_trylock_finish(UP_flags);
- batch_count = 0;
- pcp = NULL;
- locked_zone = NULL;
- }
+ batch_count++;
}
if (pcp) {
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-always-remove-pages-from-temporary-list.patch
mm-page_alloc-leave-irqs-enabled-for-per-cpu-page-allocations.patch
mm-page_alloc-leave-irqs-enabled-for-per-cpu-page-allocations-fix.patch
mm-page_alloc-simplify-locking-during-free_unref_page_list.patch
