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[140.211.169.12]) by mx.google.com with ESMTPS id br15si28528290pjb.43.2019.07.30.12.57.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Jul 2019 12:57:48 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from X1 (unknown [76.191.170.112]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 9EACF3197; Tue, 30 Jul 2019 19:57:45 +0000 (UTC) Date: Tue, 30 Jul 2019 12:57:43 -0700 From: Andrew Morton To: Catalin Marinas Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Matthew Wilcox , Qian Cai Subject: Re: [PATCH v2] mm: kmemleak: Use mempool allocations for kmemleak objects Message-Id: <20190730125743.113e59a9c449847d7f6ae7c3@linux-foundation.org> In-Reply-To: <20190727132334.9184-1-catalin.marinas@arm.com> References: <20190727132334.9184-1-catalin.marinas@arm.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 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). Why would anyone ever want to alter this? Is there some particular misbehaviour which this will improve? If so, what is it? > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2011,6 +2011,12 @@ > Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, > the default is off. > > + kmemleak.mempool= > + [KNL] Boot-time tuning of the minimum kmemleak > + metadata pool size. > + Format: > + Default: NR_CPUS * 4 > + This is the only documentation we provide people and it doesn't really explain anything at all. IOW, can we do a better job of explaining all this to the target audience? Why does the min size need to be tunable anyway?