On 01/25/2017 04:52 PM, Jens Axboe wrote:
On 01/25/2017 04:10 AM, Hannes Reinecke wrote:
[ .. ]
Bah.
Not quite. I'm still seeing some queues with state 'restart'.
I've found that I need another patch on top of that:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index e872555..edcbb44 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -753,8 +754,10 @@ static void blk_mq_timeout_work(struct work_struct
*work)
queue_for_each_hw_ctx(q, hctx, i) {
/* the hctx may be unmapped, so check it here */
- if (blk_mq_hw_queue_mapped(hctx))
+ if (blk_mq_hw_queue_mapped(hctx)) {
blk_mq_tag_idle(hctx);
+ blk_mq_sched_restart(hctx);
+ }
}
}
blk_queue_exit(q);
Reasoning is that in blk_mq_get_tag() we might end up scheduling the
request on another hctx, but the original hctx might still have the
SCHED_RESTART bit set.
Which will never cleared as we complete the request on a different hctx,
so anything we do on the end_request side won't do us any good.
I think you are right, it'll potentially trigger with shared tags and
multiple hardware queues. I'll debug this today and come up with a
decent fix.
I committed the previous patch, fwiw.
THX.
The above patch _does_ help in the sense that my testcase now completes
without stalls. And I even get a decent performance with the mq-sched
fixes: 82k IOPs sequential read with mq-deadline as compared to 44k IOPs
when running without I/O scheduling.
Still some way off from the 132k IOPs I'm getting with CFQ, but we're
getting there.
However, I do get a noticeable stall during the stonewall sequence
before the timeout handler kicks in, so the must be a better way for
handling this.
But nevertheless, thanks for all your work here.
Very much appreciated.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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