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Fri, 15 Jan 2021 11:41:09 -0800 (PST) Received: from [2620:15c:17:3:4a0f:cfff:fe51:6667] ([2620:15c:17:3:4a0f:cfff:fe51:6667]) by smtp.gmail.com with ESMTPSA id q23sm9103137pgm.89.2021.01.15.11.41.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Jan 2021 11:41:08 -0800 (PST) Date: Fri, 15 Jan 2021 11:41:07 -0800 (PST) From: David Rientjes To: Johannes Berg cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Catalin Marinas , Vlastimil Babka , Johannes Berg Subject: Re: [PATCH v2] mm/slub: disable user tracing for kmemleak caches by default In-Reply-To: <20210113215114.d94efa13ba30.I117b6764e725b3192318bbcf4269b13b709539ae@changeid> Message-ID: References: <20210113215114.d94efa13ba30.I117b6764e725b3192318bbcf4269b13b709539ae@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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, 13 Jan 2021, Johannes Berg wrote: > From: Johannes Berg > > If kmemleak is enabled, it uses a kmem cache for its own objects. > These objects are used to hold information kmemleak uses, including > a stack trace. If slub_debug is also turned on, each of them has > *another* stack trace, so the overhead adds up, and on my tests (on > ARCH=um, admittedly) 2/3rds of the allocations end up being doing > the stack tracing. > > Turn off SLAB_STORE_USER if SLAB_NOLEAKTRACE was given, to avoid > storing the essentially same data twice. > > Signed-off-by: Johannes Berg Acked-by: David Rientjes > --- > Perhaps instead it should go the other way around, and kmemleak > could even use/access the stack trace that's already in there ... > But I don't really care too much, I can just turn off slub debug > for the kmemleak caches via the command line anyway :-) > I think making the change to kmem_cache_flags() is likely the simplest.