On Wed, 30 May 2012 13:08:27 +0200
Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Wed, 2012-05-30 at 19:43 +0900, Hiroaki SHIMODA wrote:
>
> > While examining ping problem, below pattern is often 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), if I read the comment correctly, all_prev_completed becomes
> > true and limit should be increased. But POSDIFF() ignores
> > (A == B) case, so limit is decreased.
>
> Which POSDIFF(), because there are many ;)
I mean,
all_prev_completed = POSDIFF(completed, dql->prev_num_queued);
> By the way, given complexity of this I suggest you split your ideas in
> independent patches.
In this case, here is the patch what I thinking.
diff --git 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) ((A) > (B) ? (A) - (B) : 0)
+#define #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)) {
> Mabe we should change all POSDIFF(), not selected ones.
>
> #define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
>
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