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Wed, 03 Mar 2021 07:15:01 -0800 (PST) Received: from localhost ([2620:10d:c091:480::1:5636]) by smtp.gmail.com with ESMTPSA id r10sm11403961qtb.26.2021.03.03.07.15.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Mar 2021 07:15:01 -0800 (PST) Date: Wed, 3 Mar 2021 10:14:58 -0500 From: Johannes Weiner To: Muchun Song Cc: guro@fb.com, mhocko@kernel.org, akpm@linux-foundation.org, shakeelb@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2] mm: memcontrol: fix kernel stack account Message-ID: References: <20210303093956.72318-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303093956.72318-1-songmuchun@bytedance.com> X-Stat-Signature: if1mhj99t6furug11ri9zk49ia5y5c77 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BA8E120053C9 Received-SPF: none (cmpxchg.org>: No applicable sender policy available) receiver=imf28; identity=mailfrom; envelope-from=""; helo=mail-qk1-f178.google.com; client-ip=209.85.222.178 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614784502-871054 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, Mar 03, 2021 at 05:39:56PM +0800, Muchun Song wrote: > For simplification 991e7673859e ("mm: memcontrol: account kernel stack > per node") has changed the per zone vmalloc backed stack pages > accounting to per node. By doing that we have lost a certain precision > because those pages might live in different NUMA nodes. In the end > NR_KERNEL_STACK_KB exported to the userspace might be over estimated on > some nodes while underestimated on others. > > This doesn't impose any real problem to correctnes of the kernel > behavior as the counter is not used for any internal processing but it > can cause some confusion to the userspace. > > Address the problem by accounting each vmalloc backing page to its own > node. > > Fixes: 991e7673859e ("mm: memcontrol: account kernel stack per node") > Signed-off-by: Muchun Song > Reviewed-by: Shakeel Butt With changes proposed by Shakeel and Michal, this looks good to me. Acked-by: Johannes Weiner I guess the BUG_ON() was inspired by memcg_charge_kernel_stack() - not really your fault for following that example. But yeah, please drop it from your patch. Thanks!