The patch titled
Subject: mm: page_idle_get_page() does not need lru_lock
has been added to the -mm tree. Its filename is
mm-page_idle_get_page-does-not-need-lru_lock.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-page_idle_get_page-does-not-need-lru_lock.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_idle_get_page-does-not-need-lru_lock.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: page_idle_get_page() does not need lru_lock
It is necessary for page_idle_get_page() to recheck PageLRU() after
get_page_unless_zero(), but holding lru_lock around that serves no useful
purpose, and adds to lru_lock contention: delete it.
See https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop for the
discussion that led to lru_lock there; but __page_set_anon_rmap() now uses
WRITE_ONCE(), and I see no other risk in page_idle_clear_pte_refs() using
rmap_walk() (beyond the risk of racing PageAnon->PageKsm, mostly but not
entirely prevented by page_count() check in ksm.c's write_protect_page():
that risk being shared with page_referenced() and not helped by lru_lock).
Link: https://lkml.kernel.org/r/1604566549-62481-8-git-send-email-alex.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: "Chen, Rong A" <rong.a.chen@xxxxxxxxx>
Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mika Penttilä <mika.penttila@xxxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_idle.c | 4 ----
1 file changed, 4 deletions(-)
--- a/mm/page_idle.c~mm-page_idle_get_page-does-not-need-lru_lock
+++ a/mm/page_idle.c
@@ -32,19 +32,15 @@
static struct page *page_idle_get_page(unsigned long pfn)
{
struct page *page = pfn_to_online_page(pfn);
- pg_data_t *pgdat;
if (!page || !PageLRU(page) ||
!get_page_unless_zero(page))
return NULL;
- pgdat = page_pgdat(page);
- spin_lock_irq(&pgdat->lru_lock);
if (unlikely(!PageLRU(page))) {
put_page(page);
page = NULL;
}
- spin_unlock_irq(&pgdat->lru_lock);
return page;
}
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-page_idle_get_page-does-not-need-lru_lock.patch
mm-lru-revise-the-comments-of-lru_lock.patch
