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[61.68.227.232]) by smtp.gmail.com with ESMTPSA id u4sm3528397pjg.55.2020.11.25.16.35.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 16:35:46 -0800 (PST) Date: Thu, 26 Nov 2020 11:35:43 +1100 From: Balbir Singh To: Peter Zijlstra Cc: "Joel Fernandes (Google)" , Nishanth Aravamudan , Julien Desfossez , Tim Chen , Vineeth Pillai , Aaron Lu , Aubrey Li , tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , vineeth@bitbyteword.org, Chen Yu , Christian Brauner , Agata Gruza , Antonio Gomez Iglesias , graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com, pjt@google.com, rostedt@goodmis.org, derkling@google.com, benbjiang@tencent.com, Alexandre Chartre , James.Bottomley@hansenpartnership.com, OWeisse@umich.edu, Dhaval Giani , Junaid Shahid , jsbarnes@google.com, chris.hyser@oracle.com, Ben Segall , Josh Don , Hao Luo , Tom Lendacky , Aubrey Li , "Paul E. McKenney" , Tim Chen Subject: Re: [PATCH -tip 04/32] sched: Core-wide rq->lock Message-ID: <20201126003543.GG163610@balbir-desktop> References: <20201117232003.3580179-1-joel@joelfernandes.org> <20201117232003.3580179-5-joel@joelfernandes.org> <20201122091152.GB110669@balbir-desktop> <20201124081617.GT3021@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201124081617.GT3021@hirez.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 24, 2020 at 09:16:17AM +0100, Peter Zijlstra wrote: > On Sun, Nov 22, 2020 at 08:11:52PM +1100, Balbir Singh wrote: > > On Tue, Nov 17, 2020 at 06:19:34PM -0500, Joel Fernandes (Google) wrote: > > > From: Peter Zijlstra > > > > > > Introduce the basic infrastructure to have a core wide rq->lock. > > > > > > > Reading through the patch, it seems like all the CPUs have to be > > running with sched core enabled/disabled? Is it possible to have some > > cores with core sched disabled? > > Yep, patch even says so: > > + * XXX entirely possible to selectively enable cores, don't bother for now. Yes, it does in the comments, I looked at just the changelog :) > > > I don't see a strong use case for it, > > but I am wondering if the design will fall apart if that assumption is > > broken? > > The use-case I have is not using stop-machine. That is, stopping a whole > core at a time, instead of the whole sodding machine. It's on the todo > list *somewhere*.... > > Good to know, I guess that would need a transition of the entire core to idle and maintenance of a mask that prevents tasks that need core scheduling from getting off of CPUs that enable core scheduling. Balbir Singh.