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Tsirkin" , Hanna Reitz , aliang@redhat.com, qinwang@redhat.com Subject: Re: [PATCH v2 1/2] qdev: add IOThreadVirtQueueMappingList property type Message-ID: References: <20230918161604.1400051-1-stefanha@redhat.com> <20230918161604.1400051-2-stefanha@redhat.com> <87msugah6x.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87msugah6x.fsf@pond.sub.org> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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 Am 11.12.2023 um 16:32 hat Markus Armbruster geschrieben: > Kevin Wolf writes: > > > Am 18.09.2023 um 18:16 hat Stefan Hajnoczi geschrieben: > >> virtio-blk and virtio-scsi devices will need a way to specify the > >> mapping between IOThreads and virtqueues. At the moment all virtqueues > >> are assigned to a single IOThread or the main loop. This single thread > >> can be a CPU bottleneck, so it is necessary to allow finer-grained > >> assignment to spread the load. > >> > >> Introduce DEFINE_PROP_IOTHREAD_VQ_MAPPING_LIST() so devices can take a > >> parameter that maps virtqueues to IOThreads. The command-line syntax for > >> this new property is as follows: > >> > >> --device '{"driver":"foo","iothread-vq-mapping":[{"iothread":"iothread0","vqs":[0,1,2]},...]}' > >> > >> IOThreads are specified by name and virtqueues are specified by 0-based > >> index. > >> > >> It will be common to simply assign virtqueues round-robin across a set > >> of IOThreads. A convenient syntax that does not require specifying > >> individual virtqueue indices is available: > >> > >> --device '{"driver":"foo","iothread-vq-mapping":[{"iothread":"iothread0"},{"iothread":"iothread1"},...]}' > >> > >> Signed-off-by: Stefan Hajnoczi > > > > When testing this, Qing Wang noticed that "info qtree" crashes. This is > > because the string output visitor doesn't support structs. I suppose > > IOThreadVirtQueueMapping is the first struct type that is used in a qdev > > property type. > > > > So we'll probably have to add some kind of struct support to the string > > output visitor before we can apply this. Even if it's as stupid as just > > printing "" without actually displaying > > the value. > > The string visitors have been nothing but trouble. > > For input, we can now use keyval_parse() and the QObject input visitor > instead. Comes with restrictions, but I'd argue it's a more solid base > than the string input visitor. > > Perhaps we can do something similar for output: create a suitable > formatter for use it with the QObject output visitor, replacing the > string output visitor. dump_qobject() frm block/qapi.c? But I wouldn't like to block this series for a major rework of "info qtree", so I think we need to make sure that the string input visitor doesn't crash at least. Kevin