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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70eeac70b21sm3695138b3a.51.2024.07.30.18.36.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jul 2024 18:36:29 -0700 (PDT) Sender: Tejun Heo Date: Tue, 30 Jul 2024 15:36:27 -1000 From: Tejun Heo To: Peter Zijlstra Cc: Linus Torvalds , linux-kernel@vger.kernel.org, David Vernet , Ingo Molnar , Alexei Starovoitov , Thomas Gleixner Subject: Re: [GIT PULL] sched_ext: Initial pull request for v6.11 Message-ID: References: <20240723163358.GM26750@noisy.programming.kicks-ass.net> <20240724085221.GO26750@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240724085221.GO26750@noisy.programming.kicks-ass.net> Hello, On Wed, Jul 24, 2024 at 10:52:21AM +0200, Peter Zijlstra wrote: ... > So pick_task() came from the SCHED_CORE crud, which does a remote pick > and as such isn't able to do a put -- remote is still running its > current etc. > > So pick_task() *SHOULD* already be considering its current and pick > that if it is a better candidate than whatever is on the queue. > > If we have a pick_task() that doesn't do that, it's a pre-existing bug > and needs fixing anyhow. Right, I don't think it affects SCX in any significant way. Either way should be fine. ... > > Yeah, this came up before. On UP, SCX either needs to call the balance > > callback as that's where the whole dispatch logic is called from (which > > makes sense for it as dispatching often involves balancing operations), or > > SCX itself needs to call it directly in a matching sequence. Just enabling > > balance callback on UP && SCX would be the cleanest. > > Or make scx hard depend on SMP? Are there really still people using !SMP > -- and I suppose more importantly, do we care? > > I mean, they could always run an SMP kernel on their UP potato if they > *really* feel they need this. Maybe, but at the same time, it's also just some isolated cruft that enables UP support, so both sides of the scale seem similarly light-weight? I lean towards "why not support it?" but don't feel particularly strongly about it. Thanks. -- tejun