From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59892) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bN3D9-0007k1-3Q for qemu-devel@nongnu.org; Tue, 12 Jul 2016 15:19:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bN3D4-0005tU-L0 for qemu-devel@nongnu.org; Tue, 12 Jul 2016 15:19:15 -0400 References: <1468345431-106198-1-git-send-email-vsementsov@virtuozzo.com> From: Vladimir Sementsov-Ogievskiy Message-ID: <578542A8.7040903@virtuozzo.com> Date: Tue, 12 Jul 2016 22:19:04 +0300 MIME-Version: 1.0 In-Reply-To: <1468345431-106198-1-git-send-email-vsementsov@virtuozzo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qcow2: do not allocate extra memory List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: mreitz@redhat.com, kwolf@redhat.com, stefanha@redhat.com, eblake@redhat.com, den@openvz.org, fabrice@bellard.org add Fabrice Bellard On 12.07.2016 20:43, Vladimir Sementsov-Ogievskiy wrote: > There are no needs to allocate more than one cluster, as we set > avail_out for deflate to one cluster. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > > Hi all! > > Please, can anybody say me what I'm missing? > > I've looked through deflate documentation at > http://www.zlib.net/manual.html, and I didn't find anything about > allocating more memory for out buffer than specified in avail_out > field.. What is this magic formula? > > ======== > > All uses of out_buf in the function: > > uint8_t *out_buf; > ... > out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); > ... > strm.avail_out = s->cluster_size; > strm.next_out = out_buf; > > ret = deflate(&strm, Z_FINISH); > ... > out_len = strm.next_out - out_buf; > ... > ret = bdrv_pwrite(bs->file, cluster_offset, out_buf, out_len); > ... > g_free(out_buf); > > block/qcow.c | 2 +- > block/qcow2.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/qcow.c b/block/qcow.c > index ac849bd..d8826f3 100644 > --- a/block/qcow.c > +++ b/block/qcow.c > @@ -983,7 +983,7 @@ static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num, > return ret; > } > > - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); > + out_buf = g_malloc(s->cluster_size); > > /* best compression, small window, no zlib header */ > memset(&strm, 0, sizeof(strm)); > diff --git a/block/qcow2.c b/block/qcow2.c > index a5ea19b..b1c90ae 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -2612,7 +2612,7 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, > return ret; > } > > - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); > + out_buf = g_malloc(s->cluster_size); > > /* best compression, small window, no zlib header */ > memset(&strm, 0, sizeof(strm)); -- Best regards, Vladimir