From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39900) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bN1jc-0006Qo-V0 for qemu-devel@nongnu.org; Tue, 12 Jul 2016 13:44:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bN1jX-0003gI-Gw for qemu-devel@nongnu.org; Tue, 12 Jul 2016 13:44:39 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:21639 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bN1jX-0003gD-3n for qemu-devel@nongnu.org; Tue, 12 Jul 2016 13:44:35 -0400 From: Vladimir Sementsov-Ogievskiy Date: Tue, 12 Jul 2016 20:43:51 +0300 Message-Id: <1468345431-106198-1-git-send-email-vsementsov@virtuozzo.com> Subject: [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, Vladimir Sementsov-Ogievskiy 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)); -- 1.8.3.1