From patchwork Mon Feb 15 16:19:27 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 45403 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 9E636B7C98 for ; Tue, 16 Feb 2010 03:33:26 +1100 (EST) Received: from localhost ([127.0.0.1]:60528 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nh3jQ-0007lf-2q for incoming@patchwork.ozlabs.org; Mon, 15 Feb 2010 11:23:32 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nh3gW-0007M3-Da for qemu-devel@nongnu.org; Mon, 15 Feb 2010 11:20:32 -0500 Received: from [199.232.76.173] (port=33672 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nh3gW-0007Lu-0l for qemu-devel@nongnu.org; Mon, 15 Feb 2010 11:20:32 -0500 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1Nh3gU-0004bK-OD for qemu-devel@nongnu.org; Mon, 15 Feb 2010 11:20:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63591) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Nh3gU-0004bE-Am for qemu-devel@nongnu.org; Mon, 15 Feb 2010 11:20:30 -0500 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o1FGKNEO027195 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 15 Feb 2010 11:20:23 -0500 Received: from localhost.localdomain (vpn1-6-194.ams2.redhat.com [10.36.6.194]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o1FGKGSc002548; Mon, 15 Feb 2010 11:20:20 -0500 From: Kevin Wolf To: qemu-devel@nongnu.org Date: Mon, 15 Feb 2010 17:19:27 +0100 Message-Id: <1266250769-5816-2-git-send-email-kwolf@redhat.com> In-Reply-To: <1266250769-5816-1-git-send-email-kwolf@redhat.com> References: <1266250769-5816-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.12 X-detected-operating-system: by monty-python.gnu.org: Genre and OS details not recognized. Cc: kwolf@redhat.com, hch@lst.de, armbru@redhat.com, gleb@redhat.com, quintela@redhat.com Subject: [Qemu-devel] [PATCH 1/3] qcow2: Factor next_refcount_table_size out X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org When the refcount table grows, it doesn't only grow by one entry but reserves some space for future refcount blocks. The algorithm to calculate the number of entries stays the same with the fixes, so factor it out before replacing the rest. Signed-off-by: Kevin Wolf --- block/qcow2-refcount.c | 34 +++++++++++++++++++++++----------- 1 files changed, 23 insertions(+), 11 deletions(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 2fdc26b..0e2ecd7 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -123,6 +123,28 @@ static int get_refcount(BlockDriverState *bs, int64_t cluster_index) return be16_to_cpu(s->refcount_block_cache[block_index]); } +/* + * Rounds the refcount table size up to avoid growing the table for each single + * refcount block that is allocated. + */ +static unsigned int next_refcount_table_size(BDRVQcowState *s, + unsigned int min_size) +{ + unsigned int refcount_table_clusters = 0; + unsigned int new_table_size = 1; + + while (min_size > new_table_size) { + if (refcount_table_clusters == 0) { + refcount_table_clusters = 1; + } else { + refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2; + } + new_table_size = refcount_table_clusters << (s->cluster_bits - 3); + } + + return new_table_size; +} + static int grow_refcount_table(BlockDriverState *bs, int min_size) { BDRVQcowState *s = bs->opaque; @@ -136,17 +158,7 @@ static int grow_refcount_table(BlockDriverState *bs, int min_size) if (min_size <= s->refcount_table_size) return 0; /* compute new table size */ - refcount_table_clusters = s->refcount_table_size >> (s->cluster_bits - 3); - for(;;) { - if (refcount_table_clusters == 0) { - refcount_table_clusters = 1; - } else { - refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2; - } - new_table_size = refcount_table_clusters << (s->cluster_bits - 3); - if (min_size <= new_table_size) - break; - } + new_table_size = next_refcount_table_size(s, min_size); #ifdef DEBUG_ALLOC2 printf("grow_refcount_table from %d to %d\n", s->refcount_table_size,