From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50468) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uz88Q-000182-ND for qemu-devel@nongnu.org; Tue, 16 Jul 2013 12:29:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uz88O-0005Gl-Oo for qemu-devel@nongnu.org; Tue, 16 Jul 2013 12:29:54 -0400 Received: from mail-qa0-x229.google.com ([2607:f8b0:400d:c00::229]:36045) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uz88O-0005Gh-J0 for qemu-devel@nongnu.org; Tue, 16 Jul 2013 12:29:52 -0400 Received: by mail-qa0-f41.google.com with SMTP id f14so2391734qak.7 for ; Tue, 16 Jul 2013 09:29:52 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Tue, 16 Jul 2013 18:29:13 +0200 Message-Id: <1373992168-26043-3-git-send-email-pbonzini@redhat.com> In-Reply-To: <1373992168-26043-1-git-send-email-pbonzini@redhat.com> References: <1373992168-26043-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH v2 02/17] cow: make writes go at a less indecent speed List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: pl@kamp.de, famz@redhat.com, stefanha@redhat.com Only sync once per write, rather than once per sector. Signed-off-by: Paolo Bonzini --- block/cow.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/block/cow.c b/block/cow.c index fa3d41f..304e4c7 100644 --- a/block/cow.c +++ b/block/cow.c @@ -106,7 +106,7 @@ static int cow_open(BlockDriverState *bs, QDict *options, int flags) * XXX(hch): right now these functions are extremely inefficient. * We should just read the whole bitmap we'll need in one go instead. */ -static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum) +static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum, bool *first) { uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8; uint8_t bitmap; @@ -117,9 +117,21 @@ static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum) return ret; } + if (bitmap & (1 << (bitnum % 8))) { + return 0; + } + + if (*first) { + ret = bdrv_flush(bs->file); + if (ret < 0) { + return ret; + } + *first = false; + } + bitmap |= (1 << (bitnum % 8)); - ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap)); + ret = bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap)); if (ret < 0) { return ret; } @@ -181,9 +193,10 @@ static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num, { int error = 0; int i; + bool first = true; for (i = 0; i < nb_sectors; i++) { - error = cow_set_bit(bs, sector_num + i); + error = cow_set_bit(bs, sector_num + i, &first); if (error) { break; } -- 1.8.3.1