linux-kernel - [PATCH 08/12] cfq-iosched: convert cfq_group

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1355524885-22719-9-git-send-email-tj@kernel.org>
Date:	Fri, 14 Dec 2012 14:41:21 -0800
From:	Tejun Heo <tj@...nel.org>
To:	lizefan@...wei.com, axboe@...nel.dk, vgoyal@...hat.com
Cc:	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, ctalbott@...gle.com, rni@...gle.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 08/12] cfq-iosched: convert cfq_group_slice() to use cfqg->vfraction

cfq_group_slice() calculates slice by taking a fraction of
cfq_target_latency according to the ratio of cfqg->weight against
service_tree->total_weight.  This currently works only because all
cfqgs are treated to be at the same level.

To prepare for proper hierarchy support, convert cfq_group_slice() to
base the calculation on cfqg->vfraction.  As cfqg->vfraction is always
a fraction of 1 and represents the fraction allocated to the cfqg with
hierarchy considered, the slice can be simply calculated by
multiplying cfqg->vfraction to cfq_target_latency (with fixed point
shift factored in).

As vfraction calculation currently treats all non-root cfqgs as
children of the root cfqg, this patch doesn't introduce noticeable
behavior difference.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 block/cfq-iosched.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 663a0f0..fd2f4b4 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -85,7 +85,6 @@ struct cfq_rb_root {
 	struct rb_root rb;
 	struct rb_node *left;
 	unsigned count;
-	unsigned total_weight;
 	u64 min_vdisktime;
 	struct cfq_ttime ttime;
 };
@@ -976,9 +975,7 @@ static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
 static inline unsigned
 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
-	struct cfq_rb_root *st = &cfqd->grp_service_tree;
-
-	return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;
+	return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
 }
 
 static inline unsigned
@@ -1270,7 +1267,6 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
 
 	cfq_update_group_weight(cfqg);
 	__cfq_group_service_tree_add(st, cfqg);
-	st->total_weight += cfqg->weight;
 
 	/*
 	 * Activate @cfqg and calculate the portion of vfraction @cfqg is
@@ -1356,7 +1352,6 @@ cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
 	}
 
 	/* remove from the service tree */
-	st->total_weight -= cfqg->weight;
 	if (!RB_EMPTY_NODE(&cfqg->rb_node))
 		cfq_rb_erase(&cfqg->rb_node, st);
 }
-- 
1.7.11.7

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/