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From: Mike Snitzer <snitzer@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-block@vger.kernel.org, axboe@kernel.dk,
	dm-devel@redhat.com, Mikulas Patocka <mpatocka@redhat.com>,
	"Alasdair G. Kergon" <agk@redhat.com>
Subject: Re: [patch 5/5] block: use a driver-specific handler for the "inflight" value
Date: Thu, 8 Nov 2018 12:07:01 -0500	[thread overview]
Message-ID: <20181108170701.GA29107@redhat.com> (raw)
In-Reply-To: <20181108145240.GA20087@infradead.org>

On Thu, Nov 08 2018 at  9:52am -0500,
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Nov 06, 2018 at 10:35:03PM +0100, Mikulas Patocka wrote:
> > Device mapper was converted to percpu inflight counters. In order to
> > display the correct values in the "inflight" sysfs file, we need a custom
> > callback that sums the percpu counters.
> 
> The attribute that calls this is per-partition, while your method
> is per-queue, so there is some impedence mismatch here.
> 
> Is there any way you could look into just making the generic code
> use percpu counters?

Discussed doing that with Jens and reported as much here:

https://www.redhat.com/archives/dm-devel/2018-November/msg00068.html

And Jens gave additional context for why yet another attempt to switch
block core's in_flight to percpu counters is doomed (having already been
proposed and rejected twice):

https://www.redhat.com/archives/dm-devel/2018-November/msg00071.html

And yes, definitely should've cc'd linux-block (now added).

Mike

WARNING: multiple messages have this Message-ID (diff)
From: Mike Snitzer <snitzer@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
	"Alasdair G. Kergon" <agk@redhat.com>,
	dm-devel@redhat.com, linux-block@vger.kernel.org,
	axboe@kernel.dk
Subject: Re: [patch 5/5] block: use a driver-specific handler for the "inflight" value
Date: Thu, 8 Nov 2018 12:07:01 -0500	[thread overview]
Message-ID: <20181108170701.GA29107@redhat.com> (raw)
In-Reply-To: <20181108145240.GA20087@infradead.org>

On Thu, Nov 08 2018 at  9:52am -0500,
Christoph Hellwig <hch@infradead.org> wrote:

> On Tue, Nov 06, 2018 at 10:35:03PM +0100, Mikulas Patocka wrote:
> > Device mapper was converted to percpu inflight counters. In order to
> > display the correct values in the "inflight" sysfs file, we need a custom
> > callback that sums the percpu counters.
> 
> The attribute that calls this is per-partition, while your method
> is per-queue, so there is some impedence mismatch here.
> 
> Is there any way you could look into just making the generic code
> use percpu counters?

Discussed doing that with Jens and reported as much here:

https://www.redhat.com/archives/dm-devel/2018-November/msg00068.html

And Jens gave additional context for why yet another attempt to switch
block core's in_flight to percpu counters is doomed (having already been
proposed and rejected twice):

https://www.redhat.com/archives/dm-devel/2018-November/msg00071.html

And yes, definitely should've cc'd linux-block (now added).

Mike

  reply	other threads:[~2018-11-08 17:07 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-06 21:35 [patch 5/5] block: use a driver-specific handler for the "inflight" value Mikulas Patocka
2018-11-08 14:52 ` Christoph Hellwig
2018-11-08 17:07   ` Mike Snitzer [this message]
2018-11-08 17:07     ` Mike Snitzer
2018-11-14 15:18     ` Christoph Hellwig
2018-11-14 15:18       ` Christoph Hellwig
2018-11-14 15:34       ` Mike Snitzer
2018-11-14 15:34         ` Mike Snitzer
2018-11-14 22:49       ` Mikulas Patocka
2018-11-14 22:49         ` Mikulas Patocka
2018-11-14 22:35   ` Mikulas Patocka

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