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Sun, 16 Aug 2020 19:03:11 -0700 (PDT) Date: Mon, 17 Aug 2020 11:03:10 +0900 From: Sergey Senozhatsky To: Will Deacon , Marc Zyngier Subject: Re: [RFC][PATCH 0/4] arm64:kvm: teach guest sched that VCPUs can be preempted Message-ID: <20200817020310.GA1210848@jagdpanzerIV.localdomain> References: <20200721041742.197354-1-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200721041742.197354-1-sergey.senozhatsky@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200816_220315_818095_9FCA5074 X-CRM114-Status: GOOD ( 13.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: joelaf@google.com, Suzuki K Poulose , linux-kernel@vger.kernel.org, Sergey Senozhatsky , James Morse , Julien Thierry , suleiman@google.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On (20/07/21 13:17), Sergey Senozhatsky wrote: > Hello, > > RFC > > We noticed that in a number of cases when we wake_up_process() > on arm64 guest we end up enqueuing that task on a preempted VCPU. The culprit > appears to be the fact that arm64 guests are not aware of VCPU preemption > as such, so when sched picks up an idle VCPU it always assumes that VCPU > is available: > > wake_up_process() > try_to_wake_up() > select_task_rq_fair() > available_idle_cpu() > vcpu_is_preempted() // return false; > > Which is, obviously, not the case. > > This RFC patch set adds a simple vcpu_is_preempted() implementation so > that scheduler can make better decisions when it search for the idle > (v)CPU. Hi, A gentle ping. -ss _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel