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 75EDD1061B1B for ; Mon, 30 Mar 2026 19:36:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w7IO7-00065X-W6; Mon, 30 Mar 2026 15:35:04 -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 1w7IO1-000658-9Q for qemu-devel@nongnu.org; Mon, 30 Mar 2026 15:34:58 -0400 Received: from mail-lf1-x134.google.com ([2a00:1450:4864:20::134]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1w7INz-00016q-Tc for qemu-devel@nongnu.org; Mon, 30 Mar 2026 15:34:57 -0400 Received: by mail-lf1-x134.google.com with SMTP id 2adb3069b0e04-5a0fc5e2c59so5608882e87.1 for ; Mon, 30 Mar 2026 12:34:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1774899294; x=1775504094; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=bftrVlRCkBO3MiDQm70utbwn7FaBGkwSQdi8+5tsnqU=; b=R9YgtUjtELhjvEqJz/s4c5TN1bGSORKWrh4j0BY3Os7ISpZULvQla+8U7V87Rw2lKS utvT2gBHlATBMLM6nosZCofcfDsnXeLEhC2vD+jHoVtEkGsY6KBVM+4GW+Nw82ATy3MJ 5VKDP/CIqG7LYexz0CIpO0ourN9uTU2E1bhhOTPV8GVJTor6FOPbEMnWg6w6bVOhTphz z0v944J6PiFvcO+i5bH6BvB6aOVdhDHpcrTlNIikvHeOvdXmvXOuh4bhUWUFxuFzRREm amcGdc1xS4qLXEq/BO+0vXf16nONgdelgXpPdeu6aKyr/4J1PsFpo6Nor6Zi616HruGH lE0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774899294; x=1775504094; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=bftrVlRCkBO3MiDQm70utbwn7FaBGkwSQdi8+5tsnqU=; b=XZBDG27SCwrW173tgH4mvazoaDWdOsU2+LUhat2u6Frzfhik2Purq8k3C7a83fyEFy u6sFQ/CQrWmWOaEliEGLDfR86ePIt3aWxxTeVHbwjL5ikCbR6BH8U8AKOku6VnnqLbZw RINiXfv3NaDP2H90XDnhPSdOC11g8pn1V5wAubKQbyd98Q/jWwF3yw0FefPqNc4nYFCR VYcZ+hGtpP8OvUBW9ERE3NeO46MyL0qYpp0gPoK6q3ba3PC9njyWJQXJgMnzl6amF9KO ds/mTdaUQBlPqh2zqgN35D9QffDMWZRgU68fOHXz8dGOK3OuiIwiqf/QYpJveMG0xIgZ R2dQ== X-Gm-Message-State: AOJu0YyUzA3ppcpyng+ALI7vOsluyEke3XMHR8ecWEVYWROZPB7wLVvq Ya0DbSQ+nMY+QSg3odHTesp+x29FApEtWxqI6r/mLbbO7nCbQTky9Yo3sF03ZBf+ X-Gm-Gg: ATEYQzwUNx6Q1BderF/bS8MUmcG0hK/AuK+tjbGWzkPQmLljSWBcd5zCnLOFJ7Zz+Qr +jvGLqID4jGYsj2cvEmUU8bB2McnshjMRejCpm1WTv74NeFyVmwoY3ZtT0PBM9H+uVPj1ArEGUm RQjQJzKxQ22j4RaMLOtDuJeH1V3MYlz0yEM9G7Cz+KgJNwFNP+Avv13N8gIiW2CkLzbziOWEBoB iz2kk9ekUPTiyq4yAKzvdeWy2+VcqgCs7RWivmFKUPI4F5T3jg+09Iz0OPahnQcDuRrJBbSQ/+2 FWxaU3dzgyb5hir7UEwYWn71sXZtTrmRoldZDpcy0k5tUM/AVFWnzeG9cL0H3fIxUi3Hsyuu1VO fwneOhsJkT2o2MqWmbVH3HZV8Tc9h9Mlwaif4YcNb8YucK3xgSrfEElCACTeLtMnqLUSkcF5iAR NtY4zD5/wc3WuLMNKqtYlLO6hweo12NynSiPisYbyt3Ax9oQ== X-Received: by 2002:a05:6512:6c8:b0:5a2:5b88:a8a3 with SMTP id 2adb3069b0e04-5a2ab92854fmr5097955e87.31.1774899293462; Mon, 30 Mar 2026 12:34:53 -0700 (PDT) Received: from localhost.localdomain ([89.21.130.68]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a2b13f4339sm1886198e87.12.2026.03.30.12.34.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 30 Mar 2026 12:34:52 -0700 (PDT) From: Max Makarov X-Google-Original-From: Max Makarov To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Coiby Xu , Stefano Garzarella , "Michael S . Tsirkin" , Kevin Wolf , Hanna Reitz , Max Makarov Subject: [PATCH v2] vhost-user-blk-server: fix opt_io_size=1 causing severe Windows I/O degradation Date: Mon, 30 Mar 2026 22:34:51 +0300 Message-ID: <20260330193451.76037-1-maxpain@linux.com> X-Mailer: git-send-email 2.50.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::134; envelope-from=maxpain177@gmail.com; helo=mail-lf1-x134.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: qemu development 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 The QSD vhost-user-blk export sets opt_io_size=1 and min_io_size=1 in the virtio config. These values are reported to the guest through the VPD Block Limits page as OptimalTransferLength=1 block (512 bytes) and OptimalTransferLengthGranularity=1 block. Windows respects these hints and splits all I/O into ~512-byte requests, causing ~100x sequential throughput degradation (150 MB/s instead of 15+ GB/s). Linux is unaffected as its block layer ignores these values. Set both to 0 which means "not reported" per the SCSI Block Limits VPD spec, allowing Windows to use its own optimal I/O size defaults. Signed-off-by: Max Makarov --- v2: Rebased on clean master (v1 depended on a separate size_max patch). Removed unrelated Buglink. block/export/vhost-user-blk-server.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c index e89422b..67912a3 100644 --- a/block/export/vhost-user-blk-server.c +++ b/block/export/vhost-user-blk-server.c @@ -242,8 +242,8 @@ vu_blk_initialize_config(BlockDriverState *bs, config->blk_size = cpu_to_le32(blk_size); config->size_max = cpu_to_le32(0); config->seg_max = cpu_to_le32(128 - 2); - config->min_io_size = cpu_to_le16(1); - config->opt_io_size = cpu_to_le32(1); + config->min_io_size = cpu_to_le16(0); + config->opt_io_size = cpu_to_le32(0); config->num_queues = cpu_to_le16(num_queues); config->max_discard_sectors = cpu_to_le32(VIRTIO_BLK_MAX_DISCARD_SECTORS); -- 2.53.0