From patchwork Mon Jun 27 14:47:47 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Denis V. Lunev" X-Patchwork-Id: 641101 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)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3rdXbk40jMz9sBf for ; Tue, 28 Jun 2016 01:17:06 +1000 (AEST) Received: from localhost ([::1]:59265 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bHYHY-0008Ff-D8 for incoming@patchwork.ozlabs.org; Mon, 27 Jun 2016 11:17:04 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35510) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bHXpZ-0006Zq-LY for qemu-devel@nongnu.org; Mon, 27 Jun 2016 10:48:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bHXpW-0000M8-5C for qemu-devel@nongnu.org; Mon, 27 Jun 2016 10:48:08 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:27178 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bHXpV-0000FC-M1 for qemu-devel@nongnu.org; Mon, 27 Jun 2016 10:48:06 -0400 Received: from irbis.sw.ru ([10.24.38.119]) by relay.sw.ru (8.13.4/8.13.4) with ESMTP id u5RElnUK018065; Mon, 27 Jun 2016 17:47:55 +0300 (MSK) From: "Denis V. Lunev" To: qemu-block@nongnu.org, qemu-devel@nongnu.org Date: Mon, 27 Jun 2016 17:47:47 +0300 Message-Id: <1467038869-11538-2-git-send-email-den@openvz.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1467038869-11538-1-git-send-email-den@openvz.org> References: <1467038869-11538-1-git-send-email-den@openvz.org> X-detected-operating-system: by eggs.gnu.org: OpenBSD 3.x X-Received-From: 195.214.232.25 Subject: [Qemu-devel] [PATCH v4 1/3] block: ignore flush requests when storage is clean X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Fam Zheng , Evgeny Yakovlev , Max Reitz , Stefan Hajnoczi , den@openvz.org, John Snow Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Evgeny Yakovlev Some guests (win2008 server for example) do a lot of unnecessary flushing when underlying media has not changed. This adds additional overhead on host when calling fsync/fdatasync. This change introduces a dirty flag in BlockDriverState which is set in bdrv_set_dirty and is checked in bdrv_co_flush. This allows us to avoid unnecessary flushing when storage is clean. The problem with excessive flushing was found by a performance test which does parallel directory tree creation (from 2 processes). Results improved from 0.424 loops/sec to 0.432 loops/sec. Each loop creates 10^3 directories with 10 files in each. Signed-off-by: Evgeny Yakovlev Signed-off-by: Denis V. Lunev CC: Kevin Wolf CC: Max Reitz CC: Stefan Hajnoczi CC: Fam Zheng CC: John Snow --- block.c | 1 + block/dirty-bitmap.c | 3 +++ block/io.c | 19 +++++++++++++++++++ include/block/block_int.h | 1 + 4 files changed, 24 insertions(+) diff --git a/block.c b/block.c index 947df29..68ae3a0 100644 --- a/block.c +++ b/block.c @@ -2581,6 +2581,7 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset) ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS); bdrv_dirty_bitmap_truncate(bs); bdrv_parent_cb_resize(bs); + bs->dirty = true; /* file node sync is needed after truncate */ } return ret; } diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c index 4902ca5..54e0413 100644 --- a/block/dirty-bitmap.c +++ b/block/dirty-bitmap.c @@ -370,6 +370,9 @@ void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, } hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors); } + + /* Set global block driver dirty flag even if bitmap is disabled */ + bs->dirty = true; } /** diff --git a/block/io.c b/block/io.c index b9e53e3..152f5a9 100644 --- a/block/io.c +++ b/block/io.c @@ -2247,6 +2247,25 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs) goto flush_parent; } + /* Check if storage is actually dirty before flushing to disk */ + if (!bs->dirty) { + /* Flush requests are appended to tracked request list in order so that + * most recent request is at the head of the list. Following code uses + * this ordering to wait for the most recent flush request to complete + * to ensure that requests return in order */ + BdrvTrackedRequest *prev_req; + QLIST_FOREACH(prev_req, &bs->tracked_requests, list) { + if (prev_req == &req || prev_req->type != BDRV_TRACKED_FLUSH) { + continue; + } + + qemu_co_queue_wait(&prev_req->wait_queue); + break; + } + goto flush_parent; + } + bs->dirty = false; + BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK); if (bs->drv->bdrv_co_flush_to_disk) { ret = bs->drv->bdrv_co_flush_to_disk(bs); diff --git a/include/block/block_int.h b/include/block/block_int.h index 0432ba5..59a7def 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -435,6 +435,7 @@ struct BlockDriverState { bool valid_key; /* if true, a valid encryption key has been set */ bool sg; /* if true, the device is a /dev/sg* */ bool probed; /* if true, format was probed rather than specified */ + bool dirty; /* if true, media is dirty and should be flushed */ int copy_on_read; /* if nonzero, copy read backing sectors into image. note this is a reference count */