Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On Thu, Jan 18, 2018 at 05:49:10PM -0700, Jens Axboe wrote: > On 1/18/18 5:35 PM, Ming Lei wrote: > > On Thu, Jan 18, 2018 at 05:24:29PM -0700, Jens Axboe wrote: > >> On 1/18/18 5:18 PM, Ming Lei wrote: > >>> On Fri, Jan 19, 2018 at 12:14:24AM +, Bart Van Assche wrote: > On Fri,

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On 1/18/18 5:35 PM, Ming Lei wrote: > On Thu, Jan 18, 2018 at 05:24:29PM -0700, Jens Axboe wrote: >> On 1/18/18 5:18 PM, Ming Lei wrote: >>> On Fri, Jan 19, 2018 at 12:14:24AM +, Bart Van Assche wrote: On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote: > On Thu, Jan 18, 2018 at

Re: dm rq: Avoid that request processing stalls sporadically

On Fri, 2018-01-19 at 08:26 +0800, Ming Lei wrote: > No, this case won't return BLK_STS_RESOURCE. It's possible that my attempt to reverse engineer the latest blk-mq changes was wrong. But the queue stall is real and needs to be fixed. Bart.

Re: dm rq: Avoid that request processing stalls sporadically

On Thu, Jan 18, 2018 at 05:13:53PM +, Bart Van Assche wrote: > On Thu, 2018-01-18 at 11:50 -0500, Mike Snitzer wrote: > > The issue you say it was originally intended to fix _should_ be > > addressed with this change: > >

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On 1/18/18 5:18 PM, Ming Lei wrote: > On Fri, Jan 19, 2018 at 12:14:24AM +, Bart Van Assche wrote: >> On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote: >>> On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote: diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On Fri, 2018-01-19 at 08:18 +0800, Ming Lei wrote: > On Fri, Jan 19, 2018 at 12:14:24AM +, Bart Van Assche wrote: > > On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote: > > > On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote: > > > > diff --git a/drivers/md/dm-rq.c

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On Fri, Jan 19, 2018 at 12:14:24AM +, Bart Van Assche wrote: > On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote: > > On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote: > > > diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c > > > index f16096af879a..c59c59cfd2a5 100644 > > >

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote: > On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote: > > diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c > > index f16096af879a..c59c59cfd2a5 100644 > > --- a/drivers/md/dm-rq.c > > +++ b/drivers/md/dm-rq.c > > @@ -761,6 +761,7

Re: [PATCH] dm rq: Avoid that request processing stalls sporadically

On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote: > If the .queue_rq() implementation of a block driver returns > BLK_STS_RESOURCE then that block driver is responsible for > rerunning the queue once the condition that caused it to return > BLK_STS_RESOURCE has been cleared. The

Re: dm rq: Avoid that request processing stalls sporadically

On Thu, 2018-01-18 at 11:50 -0500, Mike Snitzer wrote: > The issue you say it was originally intended to fix _should_ be > addressed with this change: > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.16=4dd6edd23e7ea971efddc303f9e67eb79e95808e Hello

Re: dm rq: Avoid that request processing stalls sporadically

On Thu, Jan 18 2018 at 11:37am -0500, Bart Van Assche wrote: > If the .queue_rq() implementation of a block driver returns > BLK_STS_RESOURCE then that block driver is responsible for > rerunning the queue once the condition that caused it to return > BLK_STS_RESOURCE has

[PATCH] dm rq: Avoid that request processing stalls sporadically

If the .queue_rq() implementation of a block driver returns BLK_STS_RESOURCE then that block driver is responsible for rerunning the queue once the condition that caused it to return BLK_STS_RESOURCE has been cleared. The dm-mpath driver tells the dm core to requeue a request if e.g. not enough

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Fri, Apr 14, 2017 at 05:12:50PM +, Bart Van Assche wrote: > On Fri, 2017-04-14 at 09:13 +0800, Ming Lei wrote: > > On Thu, Apr 13, 2017 at 09:59:57AM -0700, Bart Van Assche wrote: > > > On 04/12/17 19:20, Ming Lei wrote: > > > > On Wed, Apr 12, 2017 at 06:38:07PM +, Bart Van Assche

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Fri, 2017-04-14 at 09:13 +0800, Ming Lei wrote: > On Thu, Apr 13, 2017 at 09:59:57AM -0700, Bart Van Assche wrote: > > On 04/12/17 19:20, Ming Lei wrote: > > > On Wed, Apr 12, 2017 at 06:38:07PM +, Bart Van Assche wrote: > > > > If the blk-mq core would always rerun a hardware queue if a

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Thu, Apr 13, 2017 at 09:59:57AM -0700, Bart Van Assche wrote: > On 04/12/17 19:20, Ming Lei wrote: > > On Wed, Apr 12, 2017 at 06:38:07PM +, Bart Van Assche wrote: > >> If the blk-mq core would always rerun a hardware queue if a block driver > >> returns BLK_MQ_RQ_QUEUE_BUSY then that would

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On 04/12/17 19:20, Ming Lei wrote: > On Wed, Apr 12, 2017 at 06:38:07PM +, Bart Van Assche wrote: >> If the blk-mq core would always rerun a hardware queue if a block driver >> returns BLK_MQ_RQ_QUEUE_BUSY then that would cause 100% of a single CPU core > > It won't casue 100% CPU utilization

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Wed, Apr 12, 2017 at 06:38:07PM +, Bart Van Assche wrote: > On Wed, 2017-04-12 at 11:42 +0800, Ming Lei wrote: > > On Tue, Apr 11, 2017 at 06:18:36PM +, Bart Van Assche wrote: > > > On Tue, 2017-04-11 at 14:03 -0400, Mike Snitzer wrote: > > > > Rather than working so hard to use DM code

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Wed, 2017-04-12 at 11:42 +0800, Ming Lei wrote: > On Tue, Apr 11, 2017 at 06:18:36PM +, Bart Van Assche wrote: > > On Tue, 2017-04-11 at 14:03 -0400, Mike Snitzer wrote: > > > Rather than working so hard to use DM code against me, your argument > > > should be: "blk-mq drivers X, Y and Z

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, Apr 11, 2017 at 06:18:36PM +, Bart Van Assche wrote: > On Tue, 2017-04-11 at 14:03 -0400, Mike Snitzer wrote: > > Rather than working so hard to use DM code against me, your argument > > should be: "blk-mq drivers X, Y and Z rerun the hw queue; this is a well > > established pattern" >

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, 2017-04-11 at 14:03 -0400, Mike Snitzer wrote: > Rather than working so hard to use DM code against me, your argument > should be: "blk-mq drivers X, Y and Z rerun the hw queue; this is a well > established pattern" > > I see drivers/nvme/host/fc.c:nvme_fc_start_fcp_op() does. But that

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, Apr 11 2017 at 1:51pm -0400, Bart Van Assche wrote: > On Tue, 2017-04-11 at 13:47 -0400, Mike Snitzer wrote: > > Other drivers will very likely be caught about by > > this blk-mq quirk in the future. > > Hello Mike, > > Are you aware that the requirement

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, 2017-04-11 at 13:47 -0400, Mike Snitzer wrote: > Other drivers will very likely be caught about by > this blk-mq quirk in the future. Hello Mike, Are you aware that the requirement that blk-mq drivers rerun the queue after having returned BLK_MQ_RQ_QUEUE_BUSY is a requirement that is

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, Apr 11 2017 at 12:26pm -0400, Bart Van Assche wrote: > On Tue, 2017-04-11 at 12:09 -0400, Mike Snitzer wrote: > > This has no place in dm-mq (or any blk-mq > > driver). If it is needed it should be elevated to blk-mq core to > > trigger

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Tue, 2017-04-11 at 12:09 -0400, Mike Snitzer wrote: > This has no place in dm-mq (or any blk-mq > driver). If it is needed it should be elevated to blk-mq core to > trigger blk_mq_delay_run_hw_queue() when BLK_MQ_RQ_QUEUE_BUSY is > returned from blk_mq_ops' .queue_rq. Hello Mike, If the

Re: [PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

On Fri, Apr 07 2017 at 2:16pm -0400, Bart Van Assche wrote: > While running the srp-test software I noticed that request > processing stalls sporadically at the beginning of a test, namely > when mkfs is run against a dm-mpath device. Every time when that > happened

[PATCH v4 6/6] dm rq: Avoid that request processing stalls sporadically

While running the srp-test software I noticed that request processing stalls sporadically at the beginning of a test, namely when mkfs is run against a dm-mpath device. Every time when that happened the following command was sufficient to resume request processing: echo run