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[94.245.46.49]) by smtp.gmail.com with ESMTPSA id p13sm12672000lfc.63.2020.08.11.04.10.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Aug 2020 04:10:26 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 11 Aug 2020 13:10:23 +0200 To: Michal Hocko Cc: Uladzislau Rezki , LKML , RCU , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , "Paul E . McKenney" , 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: <20200811111023.GA5544@pc636> References: <20200809204354.20137-1-urezki@gmail.com> <20200809204354.20137-2-urezki@gmail.com> <20200810123141.GF4773@dhcp22.suse.cz> <20200810160739.GA29884@pc636> <20200810192525.GG4773@dhcp22.suse.cz> <20200811091807.GA2634@pc636> <20200811102124.GH4793@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200811102124.GH4793@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 11, 2020 at 12:21:24PM +0200, Michal Hocko wrote: > On Tue 11-08-20 11:18:07, Uladzislau Rezki wrote: > > On Mon, Aug 10, 2020 at 09:25:25PM +0200, Michal Hocko wrote: > > > On Mon 10-08-20 18:07:39, Uladzislau Rezki wrote: > > > > > On Sun 09-08-20 22:43:53, Uladzislau Rezki (Sony) wrote: > [...] > > > > As i described before, calling the __get_free_page(0) with 0 as argument > > > > will solve the (a). How correctly is it? From my point of view the logic > > > > that bypass the wakeup path should be explicitly defined. > > > > > > gfp_mask == 0 is GFP_NOWAIT (aka an atomic allocation request) which > > > doesn't wake up kswapd. So if the wakeup is a problem then this would be > > > a way to go. > > > > > What do you mean Michal? gfp_mask 0 != GFP_NOWAIT: > > > > #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) > > > > it does wakeup of the kswapd. Or am i missing something? Please comment. > > If we are about to avoid the kswapd, should we define something special? > > > > #define GFP_NOWWAKE_KSWAPD 0 > > Sorry, I was more cryptic than necessary. What I meant is that > GFP_NOWAIT is the basic non-sleepable allocation. It does wake up > kswapd but a lack of it can be expressed GFP_NOWAIT & ~__GFP_KSWAPD_RECLAIM > which is 0, now. The mouthfull variant is better for future > maintainability. > OK. I got it anyway. Just decided to clarify. -- Vlad Rezki