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McKenney" , linux-mm@kvack.org Subject: [PATCH 2/2] mm: Lock PGDAT_RECLAIM_LOCKED with acquire memory ordering Date: Wed, 12 Mar 2025 10:10:14 -0400 Message-Id: <20250312141014.129725-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20250312141014.129725-1-mathieu.desnoyers@efficios.com> References: <20250312141014.129725-1-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Queue-Id: E45DE1C0022 X-Rspamd-Server: rspam08 X-Stat-Signature: ifjj3gin7j9ckanqdnst1hogg7n3t7up X-HE-Tag: 1741788622-456005 X-HE-Meta: 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 beAK3Yrx 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The PGDAT_RECLAIM_LOCKED bit is used to provide mutual exclusion of node reclaim for struct pglist_data using a single bit. Use test_and_set_bit_lock rather than test_and_set_bit to test-and-set PGDAT_RECLAIM_LOCKED with an acquire memory ordering semantic. This changes the "lock" acquisition from a full barrier to an acquire memory ordering, which is weaker. The acquire semi-permeable barrier paired with the release on unlock is sufficient for this mutual exclusion use-case. No behavior change intended other than to reduce overhead by using the appropriate barrier. Signed-off-by: Mathieu Desnoyers Cc: Andrew Morton Cc: Lorenzo Stoakes Cc: Matthew Wilcox Cc: Alan Stern Cc: Andrea Parri Cc: Will Deacon Cc: Peter Zijlstra Cc: Boqun Feng Cc: Nicholas Piggin Cc: David Howells Cc: Jade Alglave Cc: Luc Maranget Cc: "Paul E. McKenney" Cc: linux-mm@kvack.org --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index d7e27d5c24e7..021b25bdba91 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -7567,7 +7567,7 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) return NODE_RECLAIM_NOSCAN; - if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) + if (test_and_set_bit_lock(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) return NODE_RECLAIM_NOSCAN; ret = __node_reclaim(pgdat, gfp_mask, order);