From patchwork Fri Apr 9 09:46:21 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 49800 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 1861CB7CF5 for ; Fri, 9 Apr 2010 20:06:27 +1000 (EST) Received: from localhost ([127.0.0.1]:49787 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O0B2f-00088f-Nl for incoming@patchwork.ozlabs.org; Fri, 09 Apr 2010 06:02:25 -0400 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O0AoB-0004LA-GK for qemu-devel@nongnu.org; Fri, 09 Apr 2010 05:47:27 -0400 Received: from [140.186.70.92] (port=44278 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O0Ao5-0004Gp-Nm for qemu-devel@nongnu.org; Fri, 09 Apr 2010 05:47:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O0Ao2-0005we-Uo for qemu-devel@nongnu.org; Fri, 09 Apr 2010 05:47:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49171) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O0Ao2-0005w1-4A for qemu-devel@nongnu.org; Fri, 09 Apr 2010 05:47:18 -0400 Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o399l6D6019416 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 9 Apr 2010 05:47:06 -0400 Received: from localhost.localdomain (vpn1-4-18.ams2.redhat.com [10.36.4.18]) by int-mx05.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o399kvEF009943; Fri, 9 Apr 2010 05:47:04 -0400 From: Kevin Wolf To: aurelien@aurel32.net Date: Fri, 9 Apr 2010 11:46:21 +0200 Message-Id: <1270806388-28138-4-git-send-email-kwolf@redhat.com> In-Reply-To: <1270806388-28138-1-git-send-email-kwolf@redhat.com> References: <1270806388-28138-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.18 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [Qemu-devel] [STABLE][PATCH 03/10] 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. As Juan suggested take the opportunity to simplify the code a bit. Signed-off-by: Kevin Wolf Signed-off-by: Anthony Liguori (cherry picked from commit 05121aedc41f87e44e41e9cef55f2e49ce7ba94e) --- block/qcow2-refcount.c | 30 +++++++++++++++++++----------- 1 files changed, 19 insertions(+), 11 deletions(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index c2a5c04..5dde80a 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -123,6 +123,24 @@ 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 min_clusters = (min_size >> (s->cluster_bits - 3)) + 1; + unsigned int refcount_table_clusters = + MAX(1, s->refcount_table_size >> (s->cluster_bits - 3)); + + while (min_clusters > refcount_table_clusters) { + refcount_table_clusters = (refcount_table_clusters * 3 + 1) / 2; + } + + return refcount_table_clusters << (s->cluster_bits - 3); +} + static int grow_refcount_table(BlockDriverState *bs, int min_size) { BDRVQcowState *s = bs->opaque; @@ -136,17 +154,7 @@ 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,