From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8BEEE19DF45; Mon, 14 Oct 2024 10:59:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728903578; cv=none; b=qdwR+xld8jCMrM2gqkRm8aGVzPuTmeNSvVFYIzRDxr0bQsGnVJPFhrqwXRUk9AtIXu9jRVJmvX9V4HIRi0I6iYUX/SLszmtmtfcVyPMAfsg8LefDlIzCQM0ROg2/tyq7GrtivmigHJyfTMLyMwI4e5MATxuKbK3LbXJkfLJM2TU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728903578; c=relaxed/simple; bh=JMbTheclkDGS3S+GfD49eNwXVSfxy8z1/0qKFhP2pcQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lJz3lfAMed96MxFW+5/58j5+oOhlk9lqFGLjEMhXNEOtkJkJhwyxMaj63A99fAE7fVIpHRQrSOGDGmi4kLbFMEnyuKqI2yckvNn6hg6xygf1JfKRJMHrMRbWfxx26bUIv51F0Rsjlx7rpgg4wiGNGPczW21e5XjpZgVZKnfk8LA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8FB151424; Mon, 14 Oct 2024 04:00:05 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E9C283F51B; Mon, 14 Oct 2024 03:59:32 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , Anshuman Khandual , Ard Biesheuvel , Catalin Marinas , David Hildenbrand , Greg Marsden , Ivan Ivanov , Johannes Weiner , Kalesh Singh , Marc Zyngier , Mark Rutland , Matthias Brugger , Michal Hocko , Miroslav Benes , Roman Gushchin , Shakeel Butt , Will Deacon Cc: Ryan Roberts , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1 03/57] mm/memcontrol: Fix seq_buf size to save memory when PAGE_SIZE is large Date: Mon, 14 Oct 2024 11:58:10 +0100 Message-ID: <20241014105912.3207374-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241014105912.3207374-1-ryan.roberts@arm.com> References: <20241014105514.3206191-1-ryan.roberts@arm.com> <20241014105912.3207374-1-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Previously the seq_buf used for accumulating the memory.stat output was sized at PAGE_SIZE. But the amount of output is invariant to PAGE_SIZE; If 4K is enough on a 4K page system, then it should also be enough on a 64K page system, so we can save 60K om the static buffer used in mem_cgroup_print_oom_meminfo(). Let's make it so. This also has the beneficial side effect of removing a place in the code that assumed PAGE_SIZE is a compile-time constant. So this helps our quest towards supporting boot-time page size selection. Signed-off-by: Ryan Roberts --- ***NOTE*** Any confused maintainers may want to read the cover note here for context: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/ mm/memcontrol.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d563fb515766b..c5f9195f76c65 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -95,6 +95,7 @@ static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq); #define THRESHOLDS_EVENTS_TARGET 128 #define SOFTLIMIT_EVENTS_TARGET 1024 +#define SEQ_BUF_SIZE SZ_4K static inline bool task_is_dying(void) { @@ -1519,7 +1520,7 @@ void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct * void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) { /* Use static buffer, for the caller is holding oom_lock. */ - static char buf[PAGE_SIZE]; + static char buf[SEQ_BUF_SIZE]; struct seq_buf s; lockdep_assert_held(&oom_lock); @@ -1545,7 +1546,7 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) pr_info("Memory cgroup stats for "); pr_cont_cgroup_path(memcg->css.cgroup); pr_cont(":"); - seq_buf_init(&s, buf, sizeof(buf)); + seq_buf_init(&s, buf, SEQ_BUF_SIZE); memory_stat_format(memcg, &s); seq_buf_do_printk(&s, KERN_INFO); } @@ -4158,12 +4159,12 @@ static int memory_events_local_show(struct seq_file *m, void *v) int memory_stat_show(struct seq_file *m, void *v) { struct mem_cgroup *memcg = mem_cgroup_from_seq(m); - char *buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + char *buf = kmalloc(SEQ_BUF_SIZE, GFP_KERNEL); struct seq_buf s; if (!buf) return -ENOMEM; - seq_buf_init(&s, buf, PAGE_SIZE); + seq_buf_init(&s, buf, SEQ_BUF_SIZE); memory_stat_format(memcg, &s); seq_puts(m, buf); kfree(buf); -- 2.43.0