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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id d13sm6624392lfl.89.2020.08.18.08.45.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2020 08:45:05 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 18 Aug 2020 17:45:02 +0200 To: Michal Hocko Cc: "Paul E. McKenney" , Uladzislau Rezki , Peter Zijlstra , Thomas Gleixner , LKML , RCU , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Matthew Wilcox , "Theodore Y . Ts'o" , Joel Fernandes , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag Message-ID: <20200818154502.GA32169@pc636> References: <20200814180224.GQ4295@paulmck-ThinkPad-P72> <875z9lkoo4.fsf@nanos.tec.linutronix.de> <20200814204140.GT4295@paulmck-ThinkPad-P72> <20200814215206.GL3982@worktop.programming.kicks-ass.net> <20200816225655.GA17869@pc636> <20200817082849.GA28270@dhcp22.suse.cz> <20200817222803.GE23602@paulmck-ThinkPad-P72> <20200818074344.GL28270@dhcp22.suse.cz> <20200818135327.GF23602@paulmck-ThinkPad-P72> <20200818150232.GQ28270@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200818150232.GQ28270@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 566A71004E308 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: Hello, Michal. You mentioned somewhere in the thread to show figures regarding hitting a fast path and "fallback one". We follow fallback when a page allocation fails. Please see below the plot. I hope it is easy to understand: wget ftp://vps418301.ovh.net/incoming/1000000_kfree_rcu_fast_hit_vs_fallback_hit.png to summarize. When i tight loop is applied, i.e. flood simulation the fallback hit is negligible. It is a noise, out of 1 000 000 we have 1% or %2 of fallback hitting. Thanks! -- Vlad Rezki