* requests, then the request pattern is isochronous
* (see the comments on the function
* bfq_bfqq_softrt_next_start()). Thus we can compute
- * soft_rt_next_start. If, instead, the queue still
- * has outstanding requests, then we have to wait for
- * the completion of all the outstanding requests to
- * discover whether the request pattern is actually
- * isochronous.
+ * soft_rt_next_start. And we do it, unless bfqq is in
+ * interactive weight raising. We do not do it in the
+ * latter subcase, for the following reason. bfqq may
+ * be conveying the I/O needed to load a soft
+ * real-time application. Such an application will
+ * actually exhibit a soft real-time I/O pattern after
+ * it finally starts doing its job. But, if
+ * soft_rt_next_start is computed here for an
+ * interactive bfqq, and bfqq had received a lot of
+ * service before remaining with no outstanding
+ * request (likely to happen on a fast device), then
+ * soft_rt_next_start would be assigned such a high
+ * value that, for a very long time, bfqq would be
+ * prevented from being possibly considered as soft
+ * real time.
+ *
+ * If, instead, the queue still has outstanding
+ * requests, then we have to wait for the completion
+ * of all the outstanding requests to discover whether
+ * the request pattern is actually isochronous.
*/
- if (bfqq->dispatched == 0)
+ if (bfqq->dispatched == 0 &&
+ bfqq->wr_coeff != bfqd->bfq_wr_coeff)
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);
- else {
+ else if (bfqq->dispatched > 0) {
/*
* Schedule an update of soft_rt_next_start to when
* the task may be discovered to be isochronous.
* isochronous, and both requisites for this condition to hold
* are now satisfied, then compute soft_rt_next_start (see the
* comments on the function bfq_bfqq_softrt_next_start()). We
- * schedule this delayed check when bfqq expires, if it still
- * has in-flight requests.
+ * do not compute soft_rt_next_start if bfqq is in interactive
+ * weight raising (see the comments in bfq_bfqq_expire() for
+ * an explanation). We schedule this delayed update when bfqq
+ * expires, if it still has in-flight requests.
*/
if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
- RB_EMPTY_ROOT(&bfqq->sort_list))
+ RB_EMPTY_ROOT(&bfqq->sort_list) &&
+ bfqq->wr_coeff != bfqd->bfq_wr_coeff)
bfqq->soft_rt_next_start =
bfq_bfqq_softrt_next_start(bfqd, bfqq);