From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BF478C3600B for ; Thu, 27 Mar 2025 15:59:35 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1txpdZ-00082l-Ly; Thu, 27 Mar 2025 11:59:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1txpdY-00082N-3d for qemu-devel@nongnu.org; Thu, 27 Mar 2025 11:59:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1txpdW-0000Sn-Dm for qemu-devel@nongnu.org; Thu, 27 Mar 2025 11:59:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743091157; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=j/EaxZKjsouVrj5QrKUdrly+je/MOb4lndH/Ho81qbk=; b=LJhxSws72bxLOWsflnY40R2+SQYv3vt2B3rV/2vZ0WHHDbrLFaHNfvQsJQkdIWfFLf8fHU x3J1axTpjrHvqxD/cdHTH3f+VZ6CnH2CtBCTAnzQz4vHkPTnmRk2MZXd6nwaiRojVr3uZd 4WSO/7ABjyhhZ9Ge3ZJpzKXpViHH5Dk= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-43-gzFMMr_uNiqPWHgxr25B0A-1; Thu, 27 Mar 2025 11:59:14 -0400 X-MC-Unique: gzFMMr_uNiqPWHgxr25B0A-1 X-Mimecast-MFC-AGG-ID: gzFMMr_uNiqPWHgxr25B0A_1743091153 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5CDC818EBE8F; Thu, 27 Mar 2025 15:59:13 +0000 (UTC) Received: from localhost (unknown [10.2.16.93]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E6F0430001A1; Thu, 27 Mar 2025 15:59:12 +0000 (UTC) Date: Thu, 27 Mar 2025 11:59:11 -0400 From: Stefan Hajnoczi To: Hanna Czenczek Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Kevin Wolf Subject: Re: [PATCH 15/15] fuse: Increase MAX_WRITE_SIZE with a second buffer Message-ID: <20250327155911.GO37458@fedora> References: <20250325160529.117543-1-hreitz@redhat.com> <20250325160655.119407-14-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GVg2Z/JA2mxFdA7I" Content-Disposition: inline In-Reply-To: <20250325160655.119407-14-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@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_H5=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=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 --GVg2Z/JA2mxFdA7I Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 25, 2025 at 05:06:55PM +0100, Hanna Czenczek wrote: > We probably want to support larger write sizes than just 4k; 64k seems > nice. However, we cannot read partial requests from the FUSE FD, we > always have to read requests in full; so our read buffer must be large > enough to accommodate potential 64k writes if we want to support that. >=20 > Always allocating FuseRequest objects with 64k buffers in them seems > wasteful, though. But we can get around the issue by splitting the > buffer into two and using readv(): One part will hold all normal (up to > 4k) write requests and all other requests, and a second part (the > "spill-over buffer") will be used only for larger write requests. Each > FuseQueue has its own spill-over buffer, and only if we find it used > when reading a request will we move its ownership into the FuseRequest > object and allocate a new spill-over buffer for the queue. >=20 > This way, we get to support "large" write sizes without having to > allocate big buffers when they aren't used. >=20 > Also, this even reduces the size of the FuseRequest objects because the > read buffer has to have at least FUSE_MIN_READ_BUFFER (8192) bytes; but > the requests we support are not quite so large (except for >4k writes), > so until now, we basically had to have useless padding in there. >=20 > With the spill-over buffer added, the FUSE_MIN_READ_BUFFER requirement > is easily met and we can decrease the size of the buffer portion that is > right inside of FuseRequest. >=20 > As for benchmarks, the benefit of this patch can be shown easily by > writing a 4G image (with qemu-img convert) to a FUSE export: > - Before this patch: Takes 25.6 s (14.4 s with -t none) > - After this patch: Takes 4.5 s (5.5 s with -t none) >=20 > Signed-off-by: Hanna Czenczek > --- > block/export/fuse.c | 137 ++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 118 insertions(+), 19 deletions(-) Reviewed-by: Stefan Hajnoczi --GVg2Z/JA2mxFdA7I Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmfldc8ACgkQnKSrs4Gr c8jFsAf/TAlWHprBIIRNtVAbQmN+sQlUkzRhvXpKeEKq6UN7jRn01wn8912xggwG ciWpkGT5c51YmZ8IH9uYxNG6q72eN9Pt97yDyKMshjZrK5n3DK8CKSw4IzkkREAo WrM9vDRlclfttBDTXIo2/zT7SGw/566doqKtD+dsg3oQhSNewTvb30G4DI0bGYUQ spFpVojhZ+9ajD7/pnQTa6fvF2gc9SnM/Xh8QxmLIvX29EqYHxsXlKecOdSvD0sK lt/Qi/lMynPclX+fqPYm2xyZnuD/N35o3RAjzDtKY+2Yz+RD5z2Wq+fef6hFLfwk JPYVh7+UrB5Woc5pv2IWZb+gWHNqaQ== =+N/h -----END PGP SIGNATURE----- --GVg2Z/JA2mxFdA7I--