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([2001:b07:6468:f312:7841:78cc:18c6:1e20]) by smtp.gmail.com with ESMTPSA id m20sm16921540wmc.1.2020.08.06.06.47.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Aug 2020 06:47:07 -0700 (PDT) Subject: Re: [PATCH v3 0/3] aio-posix: keep aio_notify_me disabled during polling To: Stefan Hajnoczi , qemu-devel@nongnu.org References: <20200806131802.569478-1-stefanha@redhat.com> From: Paolo Bonzini Message-ID: <9115f245-dc66-50d0-a53c-c8fa2f49334b@redhat.com> Date: Thu, 6 Aug 2020 15:47:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200806131802.569478-1-stefanha@redhat.com> Content-Language: en-US Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/06 05:03:13 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fam Zheng , qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 06/08/20 15:17, Stefan Hajnoczi wrote: > v3: > * Use smp_wmb() in aio_notify_accept() [Paolo] > * Flatten if statement in aio_poll() [Paolo] > > v2: > * Added smp_mb() in aio_notify_accept() [Paolo] > * Added comments about memory barrier pairing [Paolo] > * Eliminated extra aio_compute_timeout() before calling ppoll() > > This patch series eliminates ctx->notifier EventNotifier activity when > aio_poll() is in polling mode. There is no need to use the EventNotifier since > a polling handler can detect that aio_notify() has been called by monitoring a > field in memory instead. > > Optimizing out the EventNotifier calls improves null-co random read 4KB > iodepth=1 IOPS by 18%. > > I have not modified docs/spin/aio_notify*.promela because I'm not familiar with > the SPIN model checker. > > Stefan Hajnoczi (3): > async: rename event_notifier_dummy_cb/poll() > async: always set ctx->notified in aio_notify() > aio-posix: keep aio_notify_me disabled during polling > > util/aio-posix.c | 47 +++++++++++++++++++++++++---------------------- > util/async.c | 36 +++++++++++++++++++++++------------- > 2 files changed, 48 insertions(+), 35 deletions(-) > Reviewed-by: Paolo Bonzini apart from a nit on patch 2. Paolo