The patch titled
Subject: block/cfq: cache rightmost rb_node
has been added to the -mm tree. Its filename is
block-cfq-cache-rightmost-rb_node.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/block-cfq-cache-rightmost-rb_node.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/block-cfq-cache-rightmost-rb_node.patch
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------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: block/cfq: cache rightmost rb_node
For the same reasons we already cache the leftmost pointer, apply the same
optimization for rb_last() calls. Users must explicitly do this as
rb_root_cached only deals with the smallest node.
Link: http://lkml.kernel.org/r/20170719014603.19029-18-dave@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
block/cfq-iosched.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff -puN block/cfq-iosched.c~block-cfq-cache-rightmost-rb_node block/cfq-iosched.c
--- a/block/cfq-iosched.c~block-cfq-cache-rightmost-rb_node
+++ a/block/cfq-iosched.c
@@ -94,11 +94,13 @@ struct cfq_ttime {
*/
struct cfq_rb_root {
struct rb_root_cached rb;
+ struct rb_node *rb_rightmost;
unsigned count;
u64 min_vdisktime;
struct cfq_ttime ttime;
};
#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT_CACHED, \
+ .rb_rightmost = NULL, \
.ttime = {.last_end_request = ktime_get_ns(),},}
/*
@@ -1183,6 +1185,9 @@ static struct cfq_group *cfq_rb_first_gr
static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
+ if (root->rb_rightmost == n)
+ root->rb_rightmost = rb_next(n);
+
rb_erase_cached(n, &root->rb);
RB_CLEAR_NODE(n);
@@ -1239,20 +1244,24 @@ __cfq_group_service_tree_add(struct cfq_
struct rb_node *parent = NULL;
struct cfq_group *__cfqg;
s64 key = cfqg_key(st, cfqg);
- bool leftmost = true;
+ bool leftmost = true, rightmost = true;
while (*node != NULL) {
parent = *node;
__cfqg = rb_entry_cfqg(parent);
- if (key < cfqg_key(st, __cfqg))
+ if (key < cfqg_key(st, __cfqg)) {
node = &parent->rb_left;
- else {
+ rightmost = false;
+ } else {
node = &parent->rb_right;
leftmost = false;
}
}
+ if (rightmost)
+ st->rb_rightmost = &cfqg->rb_node;
+
rb_link_node(&cfqg->rb_node, parent, node);
rb_insert_color_cached(&cfqg->rb_node, &st->rb, leftmost);
}
@@ -1355,7 +1364,7 @@ cfq_group_notify_queue_add(struct cfq_da
* so that groups get lesser vtime based on their weights, so that
* if group does not loose all if it was not continuously backlogged.
*/
- n = rb_last(&st->rb.rb_root);
+ n = st->rb_rightmost;
if (n) {
__cfqg = rb_entry_cfqg(n);
cfqg->vdisktime = __cfqg->vdisktime +
@@ -2204,7 +2213,7 @@ static void cfq_service_tree_add(struct
st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
- parent = rb_last(&st->rb.rb_root);
+ parent = st->rb_rightmost;
if (parent && parent != &cfqq->rb_node) {
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
rb_key += __cfqq->rb_key;
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
rbtree-cache-leftmost-node-internally.patch
rbtree-optimize-root-check-during-rebalancing-loop.patch
rbtree-add-some-additional-comments-for-rebalancing-cases.patch
lib-rbtree_testc-make-input-module-parameters.patch
lib-rbtree_testc-add-inorder-traversal-test.patch
lib-rbtree_testc-support-rb_root_cached.patch
sched-fair-replace-cfs_rq-rb_leftmost.patch
sched-deadline-replace-earliest-dl-and-rq-leftmost-caching.patch
locking-rtmutex-replace-top-waiter-and-pi_waiters-leftmost-caching.patch
block-cfq-replace-cfq_rb_root-leftmost-caching.patch
lib-interval_tree-fast-overlap-detection.patch
lib-interval-tree-correct-comment-wrt-generic-flavor.patch
procfs-use-faster-rb_first_cached.patch
fs-epoll-use-faster-rb_first_cached.patch
mem-memcg-cache-rightmost-node.patch
block-cfq-cache-rightmost-rb_node.patch
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