From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55103) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d3Zdf-0007He-0k for qemu-devel@nongnu.org; Wed, 26 Apr 2017 22:58:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d3Zdb-0000hz-VQ for qemu-devel@nongnu.org; Wed, 26 Apr 2017 22:58:39 -0400 From: jemmy858585@gmail.com Date: Thu, 27 Apr 2017 10:58:27 +0800 Message-Id: <1493261907-18734-1-git-send-email-lidongchen@tencent.com> Subject: [Qemu-devel] [PATCH v3] qemu-img: use blk_co_pwrite_zeroes for zero sectors when compressed List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, mreitz@redhat.com, qemu-block@nongnu.org, Lidong Chen From: Lidong Chen When the buffer is zero, blk_co_pwrite_zeroes is more effective than blk_co_pwritev with BDRV_REQ_WRITE_COMPRESSED. This patch can reduce the time for converting qcow2 images with lots of zero data. Signed-off-by: Lidong Chen --- v3 changelog: fix some spelling errors and code style. v2 changelog: unify the compressed and non-compressed code paths. --- qemu-img.c | 44 ++++++++++++++------------------------------ 1 file changed, 14 insertions(+), 30 deletions(-) diff --git a/qemu-img.c b/qemu-img.c index bbe1574..872a91b7 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -1661,6 +1661,8 @@ static int coroutine_fn convert_co_write(ImgConvertState *s, int64_t sector_num, while (nb_sectors > 0) { int n = nb_sectors; + BdrvRequestFlags flags = s->compressed ? BDRV_REQ_WRITE_COMPRESSED : 0; + switch (status) { case BLK_BACKING_FILE: /* If we have a backing file, leave clusters unallocated that are @@ -1670,43 +1672,24 @@ static int coroutine_fn convert_co_write(ImgConvertState *s, int64_t sector_num, break; case BLK_DATA: - /* We must always write compressed clusters as a whole, so don't - * try to find zeroed parts in the buffer. We can only save the - * write if the buffer is completely zeroed and we're allowed to - * keep the target sparse. */ - if (s->compressed) { - if (s->has_zero_init && s->min_sparse && - buffer_is_zero(buf, n * BDRV_SECTOR_SIZE)) - { - assert(!s->target_has_backing); - break; - } - - iov.iov_base = buf; - iov.iov_len = n << BDRV_SECTOR_BITS; - qemu_iovec_init_external(&qiov, &iov, 1); - - ret = blk_co_pwritev(s->target, sector_num << BDRV_SECTOR_BITS, - n << BDRV_SECTOR_BITS, &qiov, - BDRV_REQ_WRITE_COMPRESSED); - if (ret < 0) { - return ret; - } - break; - } - - /* If there is real non-zero data or we're told to keep the target - * fully allocated (-S 0), we must write it. Otherwise we can treat - * it as zero sectors. */ + /* If we're told to keep the target fully allocated (-S 0) or there + * is real non-zero data, we must write it. Otherwise we can treat + * it as zero sectors. + * Compressed clusters need to be written as a whole, so in that + * case we can only save the write if the buffer is completely + * zeroed. */ if (!s->min_sparse || - is_allocated_sectors_min(buf, n, &n, s->min_sparse)) + (!s->compressed && + is_allocated_sectors_min(buf, n, &n, s->min_sparse)) || + (s->compressed && + !buffer_is_zero(buf, n * BDRV_SECTOR_SIZE))) { iov.iov_base = buf; iov.iov_len = n << BDRV_SECTOR_BITS; qemu_iovec_init_external(&qiov, &iov, 1); ret = blk_co_pwritev(s->target, sector_num << BDRV_SECTOR_BITS, - n << BDRV_SECTOR_BITS, &qiov, 0); + n << BDRV_SECTOR_BITS, &qiov, flags); if (ret < 0) { return ret; } @@ -1716,6 +1699,7 @@ static int coroutine_fn convert_co_write(ImgConvertState *s, int64_t sector_num, case BLK_ZERO: if (s->has_zero_init) { + assert(!s->target_has_backing); break; } ret = blk_co_pwrite_zeroes(s->target, -- 1.8.3.1