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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a9a7a042b1sm309507285a.84.2024.09.10.07.13.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Sep 2024 07:13:36 -0700 (PDT) Date: Tue, 10 Sep 2024 10:13:34 -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 P =?utf-8?B?LiBCZXJyYW5nw6k=?= , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v2 10/17] migration/multifd: Convert multifd_send()::next_channel to atomic Message-ID: References: <76dc3ad69fa457fd1e358ad3de874474f9f64716.1724701542.git.maciej.szmigiero@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <76dc3ad69fa457fd1e358ad3de874474f9f64716.1724701542.git.maciej.szmigiero@oracle.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.145, 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, 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 Tue, Aug 27, 2024 at 07:54:29PM +0200, Maciej S. Szmigiero wrote: > From: "Maciej S. Szmigiero" > > This is necessary for multifd_send() to be able to be called > from multiple threads. > > Signed-off-by: Maciej S. Szmigiero Would it be much simpler to just use a mutex for enqueue? Something like: ===8<=== diff --git a/migration/multifd.c b/migration/multifd.c index 9b200f4ad9..979c9748b5 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -69,6 +69,8 @@ struct { QemuSemaphore channels_created; /* send channels ready */ QemuSemaphore channels_ready; + /* Mutex to serialize multifd enqueues */ + QemuMutex multifd_send_mutex; /* * Have we already run terminate threads. There is a race when it * happens that we got one error while we are exiting. @@ -305,6 +307,8 @@ bool multifd_send(MultiFDSendData **send_data) MultiFDSendParams *p = NULL; /* make happy gcc */ MultiFDSendData *tmp; + QEMU_LOCK_GUARD(&multifd_send_mutex); + if (multifd_send_should_exit()) { return false; } @@ -824,6 +828,7 @@ bool multifd_send_setup(void) multifd_send_state->params = g_new0(MultiFDSendParams, thread_count); qemu_sem_init(&multifd_send_state->channels_created, 0); qemu_sem_init(&multifd_send_state->channels_ready, 0); + qemu_mutex_init(&multifd_send_state->multifd_send_mutex); qatomic_set(&multifd_send_state->exiting, 0); multifd_send_state->ops = multifd_ops[migrate_multifd_compression()]; ===8<=== Then all the details doesn't need change (meanwhile the perf should be similar)? -- Peter Xu