Date: Fri, 22 Apr 2011 12:01:10 -0400
From: Vivek Goyal <vgoyal@redhat.com>
To: "hch@infradead.org" <hch@infradead.org>
Cc: Jens Axboe <jaxboe@fusionio.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/10] block: remove per-queue plugging
Message-ID: <20110422160110.GB8255@redhat.com>
References: <4DA2E7F0.9010904@fusionio.com>
 <20110411220505.1028816e@notabene.brown>
 <4DA2F00E.6010907@fusionio.com>
 <20110418081922.1651474a@notabene.brown>
 <4DABDC60.2090009@fusionio.com>
 <20110418172551.55629fc6@notabene.brown>
 <4DABF1EA.3070301@fusionio.com>
 <20110418183343.036f412e@notabene.brown>
 <20110418212306.GA21154@infradead.org>
 <20110422153908.GA4430@infradead.org>
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On Fri, Apr 22, 2011 at 11:39:08AM -0400, hch@infradead.org wrote:
> On Mon, Apr 18, 2011 at 05:23:06PM -0400, hch@infradead.org wrote:
> > > NeilBrown (6):
> > >       md: use new plugging interface for RAID IO.
> > >       md/dm - remove remains of plug_fn callback.
> > >       md - remove old plugging code.
> > >       md: provide generic support for handling unplug callbacks.
> > >       md: incorporate new plugging into raid5.
> > >       md: fix up raid1/raid10 unplugging.
> > 
> > Looking over more of the unplugging left over, is there a reason to
> > keep the unplug_work bits in CFQ?  They seem to rather counter the
> > current scheme (and it is the last user of kblockd outside of
> > blk-core.c)
> 
> Jens, Vivkek:
> 
> can you take a look at if cfq_schedule_dispatch is still needed in
> new unplugging world order?  It's the only kblockd user outside the
> block core that's still left, and it seems rather odd to me at least.

I guess cfq_schedule_dispatch() will still be required. One use case is
that CFQ might not dispatch requests to driver even if it has one (idling on
cfqq) and once the timer fires, it still need to be able to kick the queue
and dispatch requests.

To me this sounds independent of plugging logic. Or am I missing something.

Thanks
Vivek
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