From patchwork Tue Feb 23 15:40:52 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 46069 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 B7D94B7D01 for ; Wed, 24 Feb 2010 02:44:04 +1100 (EST) Received: from localhost ([127.0.0.1]:52580 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NjwvZ-00030G-JR for incoming@patchwork.ozlabs.org; Tue, 23 Feb 2010 10:44:01 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NjwtO-00025j-Oo for qemu-devel@nongnu.org; Tue, 23 Feb 2010 10:41:46 -0500 Received: from [199.232.76.173] (port=39457 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NjwtN-00025J-VM for qemu-devel@nongnu.org; Tue, 23 Feb 2010 10:41:46 -0500 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1NjwtL-0000pD-3n for qemu-devel@nongnu.org; Tue, 23 Feb 2010 10:41:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56578) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NjwtK-0000ox-Mo for qemu-devel@nongnu.org; Tue, 23 Feb 2010 10:41:42 -0500 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 o1NFffuA023049 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 23 Feb 2010 10:41:41 -0500 Received: from localhost.localdomain (dhcp-5-175.str.redhat.com [10.32.5.175]) by int-mx05.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id o1NFfc9J023357; Tue, 23 Feb 2010 10:41:40 -0500 From: Kevin Wolf To: qemu-devel@nongnu.org Date: Tue, 23 Feb 2010 16:40:52 +0100 Message-Id: <1266939654-26510-2-git-send-email-kwolf@redhat.com> In-Reply-To: <1266939654-26510-1-git-send-email-kwolf@redhat.com> References: <1266939654-26510-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.67 on 10.5.11.18 X-detected-operating-system: by monty-python.gnu.org: Genre and OS details not recognized. Cc: kwolf@redhat.com, quintela@redhat.com Subject: [Qemu-devel] [PATCH v2 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. As Juan suggested take the opportunity to simplify the code a bit. Signed-off-by: Kevin Wolf Acked-by: Juan Quintela --- 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 2fdc26b..933311c 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,