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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6c75e44bffesm10963556d6.3.2024.09.19.14.18.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2024 14:18:36 -0700 (PDT) Date: Thu, 19 Sep 2024 17:18:33 -0400 From: Peter Xu To: "Maciej S. Szmigiero" Cc: Fabiano Rosas , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v2 12/17] migration/multifd: Device state transfer support - send side Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Sep 19, 2024 at 09:49:57PM +0200, Maciej S. Szmigiero wrote: > On 10.09.2024 18:06, Peter Xu wrote: > > On Tue, Aug 27, 2024 at 07:54:31PM +0200, Maciej S. Szmigiero wrote: > > > +bool multifd_queue_device_state(char *idstr, uint32_t instance_id, > > > + char *data, size_t len) > > > +{ > > > + /* Device state submissions can come from multiple threads */ > > > + QEMU_LOCK_GUARD(&queue_job_mutex); > > > > Ah, just notice there's the mutex. > > > > So please consider the reply in the other thread, IIUC we can make it for > > multifd_send() to be a generic mutex to simplify the other patch too, then > > drop here. > > > > I assume the ram code should be fine taking one more mutex even without > > vfio, if it only takes once for each ~128 pages to enqueue, and only take > > in the main thread, then each update should be also in the hot path > > (e.g. no cache bouncing). > > > > Will check whether it is possible to use a common mutex here for both RAM > and device state submission without drop in performance. Thanks. -- Peter Xu