This is a note to let you know that I've just added the patch titled
bql: Avoid unneeded limit decrement.
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bql-avoid-unneeded-limit-decrement.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 666d9dab33f6e93fd3be8992b9b7453252f700f3 Mon Sep 17 00:00:00 2001
From: Hiroaki SHIMODA <[email protected]>
Date: Wed, 30 May 2012 12:25:19 +0000
Subject: bql: Avoid unneeded limit decrement.
From: Hiroaki SHIMODA <[email protected]>
[ Upstream commit 25426b794efdc70dde7fd3134dc56fac3e7d562d ]
When below pattern is observed,
TIME
dql_queued() dql_completed() |
a) initial state |
|
b) X bytes queued V
c) Y bytes queued
d) X bytes completed
e) Z bytes queued
f) Y bytes completed
a) dql->limit has already some value and there is no in-flight packet.
b) X bytes queued.
c) Y bytes queued and excess limit.
d) X bytes completed and dql->prev_ovlimit is set and also
dql->prev_num_queued is set Y.
e) Z bytes queued.
f) Y bytes completed. inprogress and prev_inprogress are true.
At f), according to the comment, all_prev_completed becomes
true and limit should be increased. But POSDIFF() ignores
(completed == dql->prev_num_queued) case, so limit is decreased.
Signed-off-by: Hiroaki SHIMODA <[email protected]>
Cc: Tom Herbert <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Denys Fedoryshchenko <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
lib/dynamic_queue_limits.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/lib/dynamic_queue_limits.c
+++ b/lib/dynamic_queue_limits.c
@@ -11,12 +11,14 @@
#include <linux/dynamic_queue_limits.h>
#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
+#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
/* Records completed count and recalculates the queue limit */
void dql_completed(struct dql *dql, unsigned int count)
{
unsigned int inprogress, prev_inprogress, limit;
- unsigned int ovlimit, all_prev_completed, completed;
+ unsigned int ovlimit, completed;
+ bool all_prev_completed;
/* Can't complete more than what's in queue */
BUG_ON(count > dql->num_queued - dql->num_completed);
@@ -26,7 +28,7 @@ void dql_completed(struct dql *dql, unsi
ovlimit = POSDIFF(dql->num_queued - dql->num_completed, limit);
inprogress = dql->num_queued - completed;
prev_inprogress = dql->prev_num_queued - dql->num_completed;
- all_prev_completed = POSDIFF(completed, dql->prev_num_queued);
+ all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
if ((ovlimit && !inprogress) ||
(dql->prev_ovlimit && all_prev_completed)) {
Patches currently in stable-queue which might be from [email protected]
are
queue-3.4/bql-avoid-possible-inconsistent-calculation.patch
queue-3.4/bql-avoid-unneeded-limit-decrement.patch
queue-3.4/bql-fix-posdiff-to-integer-overflow-aware.patch
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