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[2003:cf:d700:f306:503d:3c79:8c1b:f214]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4efe6c8f5sm21345300f8f.27.2025.06.04.06.29.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Jun 2025 06:29:25 -0700 (PDT) From: Hanna Czenczek To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Hanna Czenczek , Stefan Hajnoczi , Kevin Wolf , Markus Armbruster , Brian Song Subject: [PATCH v2 19/21] qapi/block-export: Document FUSE's multi-threading Date: Wed, 4 Jun 2025 15:28:11 +0200 Message-ID: <20250604132813.359438-20-hreitz@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250604132813.359438-1-hreitz@redhat.com> References: <20250604132813.359438-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=hreitz@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=-0.128, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Document for users that FUSE's multi-threading implementation distributes requests in a round-robin manner, regardless of where they originate from. As noted by Stefan, this will probably change with a FUSE-over-io_uring implementation (which is supposed to have CPU affinity), but documenting that is left for once that is done. Suggested-by: Stefan Hajnoczi Signed-off-by: Hanna Czenczek --- qapi/block-export.json | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/qapi/block-export.json b/qapi/block-export.json index 3ebad4ecef..f30690f54c 100644 --- a/qapi/block-export.json +++ b/qapi/block-export.json @@ -163,6 +163,11 @@ # Options for exporting a block graph node on some (file) mountpoint # as a raw image. # +# Multi-threading note: The FUSE export supports multi-threading. +# Currently, requests are distributed across these threads in a +# round-robin fashion, i.e. independently of the CPU core from which a +# request originates. +# # @mountpoint: Path on which to export the block device via FUSE. # This must point to an existing regular file. # -- 2.49.0