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Fri, 27 Jan 2023 03:43:29 -0800 (PST) Received: from hyeyoo ([114.29.91.56]) by smtp.gmail.com with ESMTPSA id x16-20020a170902b41000b001930b189b32sm2633640plr.189.2023.01.27.03.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Jan 2023 03:43:28 -0800 (PST) Date: Fri, 27 Jan 2023 20:43:20 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Michal Hocko Cc: Vlastimil Babka , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Ingo Molnar , Johannes Weiner , Shakeel Butt , Muchun Song , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Dennis Zhou , Tejun Heo Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default Message-ID: References: <20230121033942.350387-1-42.hyeyoo@gmail.com> <86e68d3b-b029-5e82-5bbc-e0ccc2ae1d36@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 0593A160015 X-Rspamd-Server: rspam01 X-Stat-Signature: h9x97h5fdecz7kn8aybcp1cnrjrytryj X-HE-Tag: 1674819810-155134 X-HE-Meta: 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 +WAbkgtd 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 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, Jan 25, 2023 at 10:51:05AM +0100, Michal Hocko wrote: > On Thu 26-01-23 00:41:15, Hyeonggon Yoo wrote: > [...] > > > Do you happen to have any perf data collected during those runs? I > > > would be interested in the memcg side of things. Maybe we can do > > > something better there. > > > > Yes, below is performance data I've collected. > > > > 6.1.8-debug-preempt-dirty > > ========================= > > Overhead Command Shared Object Symbol > > + 9.14% hackbench [kernel.vmlinux] [k] check_preemption_disabled > > Thanks! Could you just add callers that are showing in the profile for > this call please? - 14.56% 9.14% hackbench [kernel.vmlinux] [k] check_preemption_disabled - 6.37% check_preemption_disabled + 3.48% mod_objcg_state + 1.10% obj_cgroup_charge 1.02% refill_obj_stock 0.67% memcg_slab_post_alloc_hook 0.58% mod_objcg_state According to perf, many memcg functions call this function and that's because __this_cpu_xxxx checks if preemption is disabled. in include/linux/percpu-defs.h: /* * Operations for contexts that are safe from preemption/interrupts. These * operations verify that preemption is disabled. */ #define __this_cpu_read(pcp) \ ({ \ __this_cpu_preempt_check("read"); \ raw_cpu_read(pcp); \ }) #define __this_cpu_write(pcp, val) \ ({ \ __this_cpu_preempt_check("write"); \ raw_cpu_write(pcp, val); \ }) #define __this_cpu_add(pcp, val) \ ({ \ __this_cpu_preempt_check("add"); \ raw_cpu_add(pcp, val); \ }) in lib/smp_processor_id.c: noinstr void __this_cpu_preempt_check(const char *op) { check_preemption_disabled("__this_cpu_", op); } EXPORT_SYMBOL(__this_cpu_preempt_check); > -- > Michal Hocko > SUSE Labs