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Thu, 10 Oct 2024 09:57:57 +0200 Message-ID: <028501cdd2469a678df3b77c25c3cd9a1b6eff66.camel@gmx.de> Subject: Re: [PATCH 17/24] sched/fair: Implement delayed dequeue From: Mike Galbraith To: Sean Christopherson , Marek Szyprowski Cc: Peter Zijlstra , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, kprateek.nayak@amd.com, wuyun.abel@bytedance.com, youssefesmat@chromium.org, tglx@linutronix.de, kvm@vger.kernel.org Date: Thu, 10 Oct 2024 09:57:55 +0200 In-Reply-To: References: <20240727102732.960974693@infradead.org> <20240727105030.226163742@infradead.org> <5618d029-769a-4690-a581-2df8939f26a9@samsung.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:8kTllqzJiGIMIHz2BW2DTBpMUQhvY2hog/nF/iIxIqSQuuDslBb n22RNf10gAj3KNcmGsDEkIUGmAG2w+NM6cDMpARKswX99JJdXi5FjBut1aVAFejTHwvrl9T wqQgZd8G/DKiKXMBoC53zK4hnReENyS3SoLxAEflimgmU0zMPeT9RgjVEChziFXYNymYYyD xwbX6o8CRWLtM2EYUvAgg== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:QSvM6LeZu3M=;hYT6iwMLQB40f/g2d8jm1LgnNIb Cwar6Kpa+ntp/xe1qauGKPLb/maBnFAduG7YDV6OOHpWqoXeX1xkar5IVbaIizTaLZWm5jTNY grBgJ+nI9bdiGvUSonDLb/YqLvzAbHywYxhRuzLMtshh1zvgTpBpMKiNXcfhQY5Lek4AXAXxC d0fj0N4KVof6bevAg1HZH7xF3E5wo4qUMHDst4Go2MiIvO3GcSQDBpCED2PbjIrI9ucbfaXEQ sGN2rYk+B7r3ygWBi0MRDGtOffbtQbp5nOXv8wD/lY/Q8uScUqpkrIaC7EEI2RAfa3TdMwJLk 0EV3q+7asBVlKCO4CIDvLW+eDynhUVnLW/2ow2+6LM6bbaIvS5VMpB16DEHsU8KzUAPMADODp 3lr3TLy8r7CpiJqj4V4afwx367+MMBDI1VTcRBRlvCsMQirCJu++ObWHBQ7mBtni8Lu13kLfo FSH8q8pjqBwwwI27VvnpdWEakfBS1bOvKbvIfFiDkY2ETYisk9s9CrGio8Fbfj7eZmlZpe+7N AuFc6AmTYQ1OHZCOB5LqyAzWwSV0GDUstH3S5ly8d32dDit4YxTVLEJAl9S7QW37O3tx7MR4Z /k9eah/ZyGuc8WiOWM1VHk36CyEYIFWfcF6oqyK7Ev7BPYypYHctvYEzjtsEBAJyHVD6lZyU+ rwP1UiLhlR1w+woPYMxTv9mnU+N5i/TqLwxp6Q7P/NS34cZOD16R5dXnJIOO9b2HaJUQOsNOP uyXG9hhupoxp7b5hAjaggv9hN/Adkrp+rCeoEG7pSRX0d8lQonggXQwA2QBE2inAteiWPAsJi JsZoaZofnxW9e7U3eagDLYL9R4LnP1ed5c8nhSo1vuFz8= On Wed, 2024-10-09 at 19:49 -0700, Sean Christopherson wrote: > > Any thoughts on how best to handle this?=C2=A0 The below hack-a-fix reso= lves the issue, > but it's obviously not appropriate.=C2=A0 KVM uses vcpu->preempted for m= ore than just > posted interrupts, so KVM needs equivalent functionality to current->on-= rq as it > was before this commit. > > @@ -6387,7 +6390,7 @@ static void kvm_sched_out(struct preempt_notifier = *pn, > =C2=A0 > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 WRITE_ONCE(vcpu->scheduled_ou= t, true); > =C2=A0 > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (current->on_rq && vcpu->wants_= to_run) { > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (se_runnable(¤t->se) && v= cpu->wants_to_run) { > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 WRITE_ONCE(vcpu->preempted, true); > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 WRITE_ONCE(vcpu->ready, true); > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } Why is that deemed "obviously not appropriate"? ->on_rq in and of itself meaning only "on rq" doesn't seem like a bad thing. -Mike