linux-kernel - [PATCH 7/7] mm: lru_add_drain_all() do local lru_add

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Message-ID: <c50129a4-a07e-869e-604e-3952f8530316@google.com>
Date: Sun, 31 Aug 2025 02:18:39 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Will Deacon <will@...nel.org>, David Hildenbrand <david@...hat.com>, 
    Shivank Garg <shivankg@....com>, Matthew Wilcox <willy@...radead.org>, 
    Christoph Hellwig <hch@...radead.org>, Keir Fraser <keirf@...gle.com>, 
    Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>, 
    Frederick Mayle <fmayle@...gle.com>, Peter Xu <peterx@...hat.com>, 
    "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>, 
    Johannes Weiner <hannes@...xchg.org>, Vlastimil Babka <vbabka@...e.cz>, 
    Alexander Krabler <Alexander.Krabler@...a.com>, 
    Ge Yang <yangge1116@....com>, Li Zhe <lizhe.67@...edance.com>, 
    Chris Li <chrisl@...nel.org>, Yu Zhao <yuzhao@...gle.com>, 
    Axel Rasmussen <axelrasmussen@...gle.com>, 
    Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>, 
    Konstantin Khlebnikov <koct9i@...il.com>, linux-kernel@...r.kernel.org, 
    linux-mm@...ck.org
Subject: [PATCH 7/7] mm: lru_add_drain_all() do local lru_add_drain() first

No numbers to back this up, but it seemed obvious to me, that if there
are competing lru_add_drain_all()ers, the work will be minimized if each
flushes its own local queues before locking and doing cross-CPU drains.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/swap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/swap.c b/mm/swap.c
index 17438fd1f51a..4951f4d35e40 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -834,6 +834,9 @@ static inline void __lru_add_drain_all(bool force_all_cpus)
 	 */
 	this_gen = smp_load_acquire(&lru_drain_gen);
 
+	/* It helps everyone if we do our own local drain immediately. */
+	lru_add_drain();
+
 	mutex_lock(&lock);
 
 	/*
-- 
2.51.0