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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id n27sm23088492qkk.35.2019.07.31.07.54.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jul 2019 07:54:05 -0700 (PDT) Message-ID: <1564584843.11067.36.camel@lca.pw> Subject: Re: [PATCH v2] mm: kmemleak: Use mempool allocations for kmemleak objects From: Qian Cai To: Catalin Marinas Cc: Andrew Morton , Linux-MM , linux-kernel@vger.kernel.org, Michal Hocko , Matthew Wilcox Date: Wed, 31 Jul 2019 10:54:03 -0400 In-Reply-To: <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> <20190731144839.GA17773@arrakis.emea.arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit 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, 2019-07-31 at 15:48 +0100, Catalin Marinas wrote: > 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 > > > > m.com> > > > > > > --- 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? Yes, it should be fine. > > > > > [   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. >