From patchwork Fri Dec 6 17:22:57 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 298210 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 3E6732C00A8 for ; Sat, 7 Dec 2013 06:13:33 +1100 (EST) Received: from localhost ([::1]:60599 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VozAT-00057Y-0k for incoming@patchwork.ozlabs.org; Fri, 06 Dec 2013 12:26:21 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44863) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Voz80-0001w7-SS for qemu-devel@nongnu.org; Fri, 06 Dec 2013 12:23:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Voz7u-0001vO-M0 for qemu-devel@nongnu.org; Fri, 06 Dec 2013 12:23:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51916) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Voz7u-0001vD-DZ for qemu-devel@nongnu.org; Fri, 06 Dec 2013 12:23:42 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rB6HNfN4015500 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 6 Dec 2013 12:23:41 -0500 Received: from dhcp-200-207.str.redhat.com (ovpn-116-51.ams2.redhat.com [10.36.116.51]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rB6HNAUJ012982; Fri, 6 Dec 2013 12:23:40 -0500 From: Kevin Wolf To: qemu-devel@nongnu.org Date: Fri, 6 Dec 2013 18:22:57 +0100 Message-Id: <1386350580-5666-17-git-send-email-kwolf@redhat.com> In-Reply-To: <1386350580-5666-1-git-send-email-kwolf@redhat.com> References: <1386350580-5666-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, pbonzini@redhat.com, armbru@redhat.com, stefanha@redhat.com Subject: [Qemu-devel] [RFC PATCH 16/19] block: Align requests in bdrv_co_do_pwritev() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org This patch changes bdrv_co_do_pwritev() to actually be what its name promises. If requests aren't properly aligned, it performs a RMW. Requests touching the same block are serialised against the RMW request. Further optimisation of this is possible by differentiating types of requests (concurrent reads should actually be okay here). Signed-off-by: Kevin Wolf --- block.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 85 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index b9fd5c2..23ad09d 100644 --- a/block.c +++ b/block.c @@ -2935,6 +2935,12 @@ static int coroutine_fn bdrv_co_do_pwritev(BlockDriverState *bs, BdrvRequestFlags flags) { BdrvTrackedRequest req; + /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */ + uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment); + uint8_t *head_buf = NULL; + uint8_t *tail_buf = NULL; + QEMUIOVector local_qiov; + bool use_local_qiov = false; int ret; if (!bs->drv) { @@ -2952,10 +2958,88 @@ static int coroutine_fn bdrv_co_do_pwritev(BlockDriverState *bs, bdrv_io_limits_intercept(bs, bytes << BDRV_SECTOR_BITS, true); } + /* + * Align write if necessary by performing a read-modify-write cycle. + * Pad qiov with the read parts and be sure to have a tracked request not + * only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle. + */ tracked_request_begin(&req, bs, offset, bytes, true); - ret = bdrv_aligned_pwritev(bs, &req, offset, bytes, qiov, flags); + + if (offset & (align - 1)) { + QEMUIOVector head_qiov; + struct iovec head_iov; + + mark_request_serialising(&req, align); + wait_serialising_requests(&req); + + head_buf = qemu_blockalign(bs, align); + head_iov = (struct iovec) { + .iov_base = head_buf, + .iov_len = align, + }; + qemu_iovec_init_external(&head_qiov, &head_iov, 1); + + ret = bdrv_aligned_preadv(bs, &req, offset & ~(align - 1), align, + align, &head_qiov, 0); + if (ret < 0) { + goto fail; + } + + qemu_iovec_init(&local_qiov, qiov->niov + 2); + qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1)); + qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); + use_local_qiov = true; + + bytes += offset & (align - 1); + offset = offset & ~(align - 1); + } + + if ((offset + bytes) & (align - 1)) { + QEMUIOVector tail_qiov; + struct iovec tail_iov; + size_t tail_bytes; + + mark_request_serialising(&req, align); + wait_serialising_requests(&req); + + tail_buf = qemu_blockalign(bs, align); + tail_iov = (struct iovec) { + .iov_base = tail_buf, + .iov_len = align, + }; + qemu_iovec_init_external(&tail_qiov, &tail_iov, 1); + + ret = bdrv_aligned_preadv(bs, &req, (offset + bytes) & ~(align - 1), align, + align, &tail_qiov, 0); + if (ret < 0) { + goto fail; + } + + if (!use_local_qiov) { + qemu_iovec_init(&local_qiov, qiov->niov + 1); + qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size); + use_local_qiov = true; + } + + tail_bytes = (offset + bytes) & (align - 1); + qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes); + + bytes = ROUND_UP(bytes, align); + } + + ret = bdrv_aligned_pwritev(bs, &req, offset, bytes, + use_local_qiov ? &local_qiov : qiov, + flags); + +fail: tracked_request_end(&req); + if (use_local_qiov) { + qemu_iovec_destroy(&local_qiov); + qemu_vfree(head_buf); + qemu_vfree(tail_buf); + } + return ret; }