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From: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <eag0628@gmail.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/13] workqueue: enhance locking and record global worker id for work data
Date: Tue, 5 Feb 2013 08:50:16 -0800	[thread overview]
Message-ID: <20130205165016.GB4276@mtj.dyndns.org> (raw)
In-Reply-To: <CACvQF52Lqi2TuXc9oCdGkAzxcpE12YfuX=9-jp5tePsOqPBe6w@mail.gmail.com>

Hello, Lai.

On Wed, Feb 06, 2013 at 12:19:26AM +0800, Lai Jiangshan wrote:
> > Can't we just make get_work_pool_id() do a fast path if OFFQ than
> > requiring the user to distinguish off and on queue cases?
> 
> old code, get_work_pool_id() is only called when offq.
> after series applied, offq_work_worker_id() *must* be called only when offq,
> and we can't offer get_work_worker_id().

Can you please elaborate why we can't offer get_work_worker_id()?

> > While I'm a bit worried about capping total number of workers by the
> > amount bits left in work->data, if that doesn't cause any practical
> > issue (how many do we have available on 32bit?), I think this is the
> > better approach.  We couldn't do this before because work -> worker
> > relationship could be 1:N but it should now be doable.  Note that we
> > need RCU no matter what we index (pool or worker) to avoid locking on
> > each lookup.
> 
> BUILD_BUG_ON((BITS_PER_LONG != 64) && (WORK_OFFQ_WORKER_SHIFT > 12));
> 
> Every worker needs at least 4k memory for its stack, the bits are enough if
> WORK_OFFQ_WORKER_SHIFT <= 12.

Ah, so that was what that comment was about, so we always have enough
bits.  I have to say the comment is a bit cryptic.

> > From past experience, I *think* it's gonna be a bit of struggle for
> > both of us to get the series in a shape that I would find acceptable
> > by reviewing and iterating, so I might just swallow it and regurgitate
> > into a form that I like.  Hmm.... dunno.  Will think about it.
> 
> It is not nightmare for me! the work and discusses will consume most
> time of my night, no night time for nightmare.

Heh, yeah, I didn't say it was a nightmare.  I do like your work.  I
think most problems are from communication (including description and
comments).  I guess I can help along for a while.

> > Anyways, nice work.
> >
> I'm glad you like it. My daughter was born about 3month ago and I left
> workqueue work then. I think it is time to pick up old pending
> patches.

Big congratulations.  :)

Thanks!

-- 
tejun

      reply	other threads:[~2013-02-05 16:50 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-31 18:41 [PATCH 00/13] workqueue: enhance locking and record global worker id for work data Lai Jiangshan
2013-01-31 18:41 ` [PATCH 01/13] workqueue: remove WORK_CPU_NONE Lai Jiangshan
2013-02-04 19:49   ` Tejun Heo
2013-02-05 12:03     ` Lai Jiangshan
2013-02-06 22:34   ` [PATCH wq/for-3.9] workqueue: replace WORK_CPU_NONE/LAST with WORK_CPU_END Tejun Heo
2013-01-31 18:41 ` [PATCH 02/13] workqueue: fix work_busy() Lai Jiangshan
2013-02-04 19:54   ` Tejun Heo
2013-02-05 12:06     ` Lai Jiangshan
2013-02-05 18:53       ` Tejun Heo
2013-02-06 11:42         ` Lai Jiangshan
2013-02-06 14:05           ` Tejun Heo
2013-02-06 23:02   ` [PATCH wq/for-3.9] workqueue: make work_busy() test WORK_STRUCT_PENDING first Tejun Heo
2013-01-31 18:41 ` [PATCH 03/13] workqueue: don't set work cwq until we queued it on pool Lai Jiangshan
2013-02-04 21:28   ` Tejun Heo
2013-02-05 15:00     ` Lai Jiangshan
2013-02-05 16:45       ` Tejun Heo
2013-02-06 11:35         ` Lai Jiangshan
2013-02-06 14:18           ` Tejun Heo
2013-02-05 15:06     ` Lai Jiangshan
2013-02-07  0:28   ` [PATCH wq/for-3.9 workqueue]: add delayed_work->wq to simplify reentrancy handling Tejun Heo
2013-01-31 18:41 ` [PATCH 04/13] workqueue: clear cwq when cancel the work Lai Jiangshan
2013-02-07  0:53   ` [PATCH wq/for-3.9] workqueue: make work->data point to pool after try_to_grab_pending() Tejun Heo
2013-01-31 18:41 ` [PATCH 05/13] workqueue: change queued detection and remove *mb()s Lai Jiangshan
2013-02-07  1:52   ` [PATCH wq/for-3.9] workqueue: simplify is-work-item-queued-here test Tejun Heo
2013-02-07  2:03     ` [PATCH wq/for-3.9] workqueue: cosmetic update in try_to_grab_pending() Tejun Heo
2013-01-31 18:41 ` [PATCH 06/13] workqueue: get pool id from work->data directly if it is offq Lai Jiangshan
2013-02-07 20:16   ` [PATCH wq/for-3.9] workqueue: make get_work_pool_id() cheaper Tejun Heo
2013-01-31 18:41 ` [PATCH 07/13] workqueue: get pool from wq/cwq Lai Jiangshan
2013-02-07 21:13   ` [PATCH wq/for-3.9] workqueue: pick cwq instead of pool in __queue_work() Tejun Heo
2013-01-31 18:41 ` [PATCH 08/13] workqueue: add lock_pool_executing_work() Lai Jiangshan
2013-02-04 21:34   ` Tejun Heo
2013-02-05 12:15     ` Lai Jiangshan
2013-02-05 19:09       ` Tejun Heo
2013-01-31 18:41 ` [PATCH 09/13] workqueue: add lock_pool_queued_work() Lai Jiangshan
2013-01-31 18:41 ` [PATCH 10/13] workqueue: add lock_pool_own_work() and remove get_work_pool() Lai Jiangshan
2013-02-04 21:38   ` Tejun Heo
2013-01-31 18:41 ` [PATCH 11/13] workqueue: allow more work_pool id space Lai Jiangshan
2013-01-31 18:41 ` [PATCH 12/13] workqueue: add worker's global worker ID Lai Jiangshan
2013-02-04 21:39   ` Tejun Heo
2013-01-31 18:41 ` [PATCH 13/13] workqueue: record global worker ID instead of pool ID in work->data when off-queue Lai Jiangshan
2013-02-04 21:40   ` Tejun Heo
2013-02-04 22:12   ` Tejun Heo
2013-02-05 15:18     ` Lai Jiangshan
2013-02-07 22:02   ` Tejun Heo
2013-02-13 22:23     ` Tejun Heo
2013-02-04 21:04 ` [PATCH 00/13] workqueue: enhance locking and record global worker id for work data Tejun Heo
2013-02-05 16:19   ` Lai Jiangshan
2013-02-05 16:50     ` Tejun Heo [this message]

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