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| author | Hiroaki SHIMODA <shimoda.hiroaki@gmail.com> | 2012-05-30 12:25:19 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-07-16 09:03:43 -0700 |
| commit | 1414a53d956340ca8b1b27e05ab94ba63e82ed97 (patch) | |
| tree | 816b424b7416c6e62c56f9cddc7a199b03f27afa /lib | |
| parent | 19d07e884b7fd22f92eb8939556dcbf55df1982c (diff) | |
| download | lwn-1414a53d956340ca8b1b27e05ab94ba63e82ed97.tar.gz lwn-1414a53d956340ca8b1b27e05ab94ba63e82ed97.zip | |
bql: Avoid unneeded limit decrement.
[ 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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/dynamic_queue_limits.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c index c87eb76f2fd4..0fafa77f4036 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)) { |