From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 2/2] rbd: use binary search for snapshot lookup Date: Wed, 01 May 2013 16:32:52 -0500 Message-ID: <51818A04.5040809@inktank.com> References: <51818945.1040002@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ia0-f170.google.com ([209.85.210.170]:58898 "EHLO mail-ia0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761635Ab3EAVcz (ORCPT ); Wed, 1 May 2013 17:32:55 -0400 Received: by mail-ia0-f170.google.com with SMTP id k20so1735061iak.1 for ; Wed, 01 May 2013 14:32:55 -0700 (PDT) Received: from [172.22.22.4] (c-71-195-31-37.hsd1.mn.comcast.net. [71.195.31.37]) by mx.google.com with ESMTPSA id o10sm5767182igh.2.2013.05.01.14.32.53 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 01 May 2013 14:32:54 -0700 (PDT) In-Reply-To: <51818945.1040002@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org Use bsearch(3) to make snapshot lookup by id more efficient. (There could be thousands of snapshots, and conceivably many more.) Signed-off-by: Alex Elder --- drivers/block/rbd.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 3f58aba..a6e5fe3 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include @@ -819,16 +820,39 @@ static const char *_rbd_dev_v1_snap_name(struct rbd_device *rbd_dev, u32 which) return kstrdup(snap_name, GFP_KERNEL); } +/* + * Snapshot id comparison function for use with qsort()/bsearch(). + * Note that result is for snapshots in *descending* order. + */ +static int snapid_compare_reverse(const void *s1, const void *s2) +{ + u64 snap_id1 = *(u64 *)s1; + u64 snap_id2 = *(u64 *)s2; + + if (snap_id1 < snap_id2) + return 1; + return snap_id1 == snap_id2 ? 0 : 1; +} + +/* + * Search a snapshot context to see if the given snapshot id is + * present. + * + * Returns the position of the snapshot id in the array if it's found, + * or BAD_SNAP_INDEX otherwise. + * + * Note: The snapshot array is in kept sorted (by the osd) in + * reverse order, highest snapshot id first. + */ static u32 rbd_dev_snap_index(struct rbd_device *rbd_dev, u64 snap_id) { struct ceph_snap_context *snapc = rbd_dev->header.snapc; - u32 which; + u64 *found; - for (which = 0; which < snapc->num_snaps; which++) - if (snapc->snaps[which] == snap_id) - return which; + found = bsearch(&snap_id, &snapc->snaps, snapc->num_snaps, + sizeof (snap_id), snapid_compare_reverse); - return BAD_SNAP_INDEX; + return found ? (u32)(found - &snapc->snaps[0]) : BAD_SNAP_INDEX; } static const char *rbd_dev_v1_snap_name(struct rbd_device *rbd_dev, -- 1.7.9.5