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[217.140.110.172]) by mx.google.com with ESMTP id t21si19758194edw.253.2019.07.31.07.48.43 for ; Wed, 31 Jul 2019 07:48:44 -0700 (PDT) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@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 4C7FD344; Wed, 31 Jul 2019 07:48:43 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 647DD3F694; Wed, 31 Jul 2019 07:48:42 -0700 (PDT) Date: Wed, 31 Jul 2019 15:48:40 +0100 From: Catalin Marinas To: Qian Cai Cc: Andrew Morton , Linux-MM , linux-kernel@vger.kernel.org, Michal Hocko , Matthew Wilcox Subject: Re: [PATCH v2] mm: kmemleak: Use mempool allocations for kmemleak objects Message-ID: <20190731144839.GA17773@arrakis.emea.arm.com> References: <20190727132334.9184-1-catalin.marinas@arm.com> <20190730125743.113e59a9c449847d7f6ae7c3@linux-foundation.org> <1564518157.11067.34.camel@lca.pw> <20190731095355.GC63307@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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, Jul 31, 2019 at 08:02:30AM -0400, Qian Cai wrote: > On Jul 31, 2019, at 5:53 AM, Catalin Marinas wrote: > > On Tue, Jul 30, 2019 at 04:22:37PM -0400, Qian Cai wrote: > >> On Tue, 2019-07-30 at 12:57 -0700, Andrew Morton wrote: > >>> On Sat, 27 Jul 2019 14:23:33 +0100 Catalin Marinas > >>>> --- 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 > >>>> + > >> > >> Catalin, BTW, it is right now unable to handle a large size. I tried to reserve > >> 64M (kmemleak.mempool=67108864), [...] > > It looks like the mempool cannot be created. 64M objects means a > > kmalloc(512MB) for the pool array in mempool_init_node(), so that hits > > the MAX_ORDER warning in __alloc_pages_nodemask(). > > > > Maybe the mempool tunable won't help much for your case if you need so > > many objects. It's still worth having a mempool for kmemleak but we > > could look into changing the refill logic while keeping the original > > size constant (say 1024 objects). > > Actually, kmemleak.mempool=524288 works quite well on systems I have here. This > is more of making the code robust by error-handling a large value without the > NULL-ptr-deref below. Maybe simply just validate the value by adding upper bound > to not trigger that warning with MAX_ORDER. Would it work for you with a Kconfig option, similar to DEBUG_KMEMLEAK_EARLY_LOG_SIZE? > >> [ 16.192449][ T1] BUG: Unable to handle kernel data access at 0xffffffffffffb2aa > > > > This doesn't seem kmemleak related from the trace. > > This only happens when passing a large kmemleak.mempool, e.g., 64M > > [ 16.193126][ T1] NIP [c000000000b2a2fc] log_early+0x8/0x160 > [ 16.193153][ T1] LR [c0000000003e6e48] kmem_cache_free+0x428/0x740 Ah, I missed the log_early() call here. It's a kmemleak bug where it isn't disabled properly in case of an error and log_early() is still called after the .text.init section was freed. I'll send a patch. -- Catalin