From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [158.69.130.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3172E1F4CB7 for ; Wed, 12 Mar 2025 14:10:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=158.69.130.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741788628; cv=none; b=cxBZWpXH2UXOYrhsaq7RHYjdx17brjkjVzqIW1Oja8tdev0/zNICll/cE8d+nvV5juQUbFwdlxoIXryPMi6k5XizOcB1wKDfJzUmxXRc3PlXNPUjBpijQItfH3WwFOQW3bFr3lrA0pkAKR+VG2KQbyhNyCnL3xbnci6DP+L/Vvk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741788628; c=relaxed/simple; bh=Gzhh0CL/jONkRqz2afghq1tga+QOx3jfOt+TU84UHYM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=iPJ3IT9bJ1mmw5TlDbli78EjxZaOdt7aw+UtWuoAOinuANXZaYvufs79Ab//eDrlG8mfgjh+llpjhSuKXx7T0iovC26DdlRTnGi+LiJRaevEqMWYqSCLoVyizlWPUpPvso5fviOUZyn1evmxZu1unVfXJu5iIbi3IgWtEHAQedY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=PghIbEkg; arc=none smtp.client-ip=158.69.130.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="PghIbEkg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1741788622; bh=Gzhh0CL/jONkRqz2afghq1tga+QOx3jfOt+TU84UHYM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PghIbEkgaPly51Wi3eLEuUlrqXO2ZV/nlYwIqQIaeqQJ4BWQghM6+nV4AGILwwGEP SZ8kbHdY7Dcu1VxHGEd+H7DVwc5CEnVcRvOqwhoMEWeebmiBH5SQhWL3DZcAmPWBo7 47XpB46EbA0hYJTc9ZigzmMjzRmA2epn7NmjfgKX0VfPQvdZcvxrH5EeN1w2+QJs9u +t3IVEhEFvJMTUjVE6wBsuwS37mShP6QXqUUdrMMpMaQxnzL0EntJKFiDDK5YrX4jh LjrzbnZZ6hge3vqqvRCkxKMwoQ8qgnzXAIRzbvrYGYuNixxKaJFB0nUDWTl4Ns0jTr 08ZoYYnQfW0Qw== Received: from localhost.localdomain (96-127-217-162.qc.cable.ebox.net [96.127.217.162]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4ZCXb20QB7zV0F; Wed, 12 Mar 2025 10:10:22 -0400 (EDT) From: Mathieu Desnoyers To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , Lorenzo Stoakes , Matthew Wilcox , Alan Stern , Andrea Parri , Will Deacon , Peter Zijlstra , Boqun Feng , Nicholas Piggin , David Howells , Jade Alglave , Luc Maranget , "Paul E. 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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); -- 2.25.1