path: root/lib
diff options
authorHiroaki SHIMODA <shimoda.hiroaki@gmail.com>2012-05-30 12:25:19 +0000
committerDavid S. Miller <davem@davemloft.net>2012-05-31 18:18:16 -0400
commit25426b794efdc70dde7fd3134dc56fac3e7d562d (patch)
tree800ef2d96fbf9cc6e8973d517f714edbda6b4fc2 /lib
parent0cfd32b736ae0c36b42697584811042726c07cba (diff)
bql: Avoid unneeded limit decrement.
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 <shimoda.hiroaki@gmail.com> Cc: Tom Herbert <therbert@google.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Denys Fedoryshchenko <denys@visp.net.lb> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
1 files changed, 4 insertions, 2 deletions
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index c87eb76f2fd..0fafa77f403 100644
--- 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, unsigned int count)
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)) {