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>
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@ -11,12 +11,14 @@
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#include <linux/dynamic_queue_limits.h>
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#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
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#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
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/* Records completed count and recalculates the queue limit */
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void dql_completed(struct dql *dql, unsigned int count)
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{
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unsigned int inprogress, prev_inprogress, limit;
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unsigned int ovlimit, all_prev_completed, completed;
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unsigned int ovlimit, completed;
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bool all_prev_completed;
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/* Can't complete more than what's in queue */
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BUG_ON(count > dql->num_queued - dql->num_completed);
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@ -26,7 +28,7 @@ void dql_completed(struct dql *dql, unsigned int count)
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ovlimit = POSDIFF(dql->num_queued - dql->num_completed, limit);
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inprogress = dql->num_queued - completed;
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prev_inprogress = dql->prev_num_queued - dql->num_completed;
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all_prev_completed = POSDIFF(completed, dql->prev_num_queued);
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all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
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if ((ovlimit && !inprogress) ||
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(dql->prev_ovlimit && all_prev_completed)) {
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