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Mon, 05 Jun 2023 16:24:46 -0400 X-MC-Unique: I42WB9c1NUuc32d64lbXxw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 28971802355; Mon, 5 Jun 2023 20:24:46 +0000 (UTC) Received: from localhost (unknown [10.39.192.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id B434A40CFD46; Mon, 5 Jun 2023 20:24:45 +0000 (UTC) Date: Mon, 5 Jun 2023 15:05:31 -0400 From: Stefan Hajnoczi To: Peter-Jan Gootzen Subject: Re: [PATCH V3] virtio-fs: Improved request latencies when Virtio queue is full Message-ID: <20230605190531.GD1861823@fedora> References: <20230602133224.1445655-1-peter-jan@gootzen.net> MIME-Version: 1.0 In-Reply-To: <20230602133224.1445655-1-peter-jan@gootzen.net> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Cc: miklos@szeredi.hu, vgoyal@redhat.com, virtualization@lists.linux-foundation.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============1019388564938187061==" Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" --===============1019388564938187061== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="6Pq9e+GA+AqICj6e" Content-Disposition: inline --6Pq9e+GA+AqICj6e Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 02, 2023 at 03:32:26PM +0200, Peter-Jan Gootzen wrote: > When the Virtio queue is full, a work item is scheduled > to execute in 1ms that retries adding the request to the queue. > This is a large amount of time on the scale on which a > virtio-fs device can operate. When using a DPU this is around > 40us baseline without going to a remote server (4k, QD=3D1). > This patch queues requests when the Virtio queue is full, > and when a completed request is taken off, immediately fills > it back up with queued requests. >=20 > This reduces the 99.9th percentile latencies in our tests by > 60x and slightly increases the overall throughput, when using a > queue depth 2x the size of the Virtio queue size, with a > DPU-powered virtio-fs device. >=20 > Furthermore, the virtio-fs driver now also always lets -ENOMEM > errors go to userspace instead of retrying the request in the > driver. >=20 > Signed-off-by: Peter-Jan Gootzen > --- > V3: Fixed requests falling into the void when -ENOMEM and no new > incoming requests. Virtio-fs now always lets -ENOMEM bubble up to > userspace. Also made queue full condition more explicit with > -ENOSPC in `send_forget_request`. > V2: Not scheduling dispatch work anymore when not needed > and changed delayed_work structs to work_struct structs Hi Peter-Jan, I will be traveling and will try to look at this patch as soon as possible. If Vivek and others are happy, please don't wait for me. Thanks, Stefan --6Pq9e+GA+AqICj6e Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmR+MfsACgkQnKSrs4Gr c8jC8ggArir260aKptEmDV9js9Koo/gMXoxTUjogh6iUdyq6rZEoStd3x3lAg+bG Zy9//KjWyl1v/oVJaiPIgnu6zYqrjHhc7AXssABUH7M1mR4+OwO2eebGRETdDajk 6vLT2r/imHkMdHGFDobEiuWHPijbD1B9qVj5NF56/3aZrwidNhOXuC1ZXzC+2Jbq emf1PAI6W9ncLQauWXYX5w8hRkPVzDPife31OL37Opue2CNSgbpdDl6IazTMNn/5 Ityo8E1D1icaFgHH9WFOnJQg6gksDvOLbVR1HUNbPuo1l2ZRUVgibHhbzkWO+Vc9 dglFU1P1zOl6p1YoE5Xv7y9504jvIg== =9HX/ -----END PGP SIGNATURE----- --6Pq9e+GA+AqICj6e-- --===============1019388564938187061== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization --===============1019388564938187061==--