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[195.135.220.15]) by mx.google.com with ESMTPS id l53si23985086edd.293.2019.07.31.23.41.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 23:41:55 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8003FAD1E; Thu, 1 Aug 2019 06:41:55 +0000 (UTC) Date: Thu, 1 Aug 2019 08:41:53 +0200 From: Michal Hocko To: Catalin Marinas Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Qian Cai Subject: Re: [PATCH v2] mm: kmemleak: Use mempool allocations for kmemleak objects Message-ID: <20190801064153.GD11627@dhcp22.suse.cz> References: <20190727132334.9184-1-catalin.marinas@arm.com> <20190730130215.919b31c19df935cc5f1483e6@linux-foundation.org> <20190731154450.GB17773@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190731154450.GB17773@arrakis.emea.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Wed 31-07-19 16:44:50, Catalin Marinas wrote: > On Tue, Jul 30, 2019 at 01:02:15PM -0700, Andrew Morton wrote: > > On Sat, 27 Jul 2019 14:23:33 +0100 Catalin Marinas wrote: > > > > > Add mempool allocations for struct kmemleak_object and > > > kmemleak_scan_area as slightly more resilient than kmem_cache_alloc() > > > under memory pressure. Additionally, mask out all the gfp flags passed > > > to kmemleak other than GFP_KERNEL|GFP_ATOMIC. > > > > > > A boot-time tuning parameter (kmemleak.mempool) is added to allow a > > > different minimum pool size (defaulting to NR_CPUS * 4). > > > > btw, the checkpatch warnings are valid: > > > > WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc > > #70: FILE: mm/kmemleak.c:197: > > +static int min_object_pool = NR_CPUS * 4; > > > > WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc > > #71: FILE: mm/kmemleak.c:198: > > +static int min_scan_area_pool = NR_CPUS * 1; > > > > There can be situations where NR_CPUS is much larger than > > num_possible_cpus(). Can we initialize these tunables within > > kmemleak_init()? > > We could and, at least on arm64, cpu_possible_mask is already > initialised at that point. However, that's a totally made up number. I > think we would better go for a Kconfig option (defaulting to, say, 1024) > similar to the CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE and we grow it if > people report better values in the future. If you really want/need to make this configurable then the command line parameter makes more sense - think of distribution kernel users for example. But I am still not sure why this is really needed. The initial size is a "made up" number of course. There is no good estimation to make (without a crystal ball). The value might be increased based on real life usage. -- Michal Hocko SUSE Labs