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From: Andy Walls <awalls@md.metrocast.net>
To: Tejun Heo <tj@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
Subject: Re: [PATCH 11/32] v4l/cx18: update workqueue usage
Date: Tue, 04 Jan 2011 08:21:35 -0500	[thread overview]
Message-ID: <1294147295.2107.14.camel@morgan.silverblock.net> (raw)
In-Reply-To: <20110104083637.GB8066@mtj.dyndns.org>

On Tue, 2011-01-04 at 09:36 +0100, Tejun Heo wrote:
> Hello,
> 
> On Mon, Jan 03, 2011 at 07:54:56PM -0500, Andy Walls wrote:
> > 2. To prevent work items being handled by keventd/n from being delayed
> > too long, as the deferred work in question can involve a bit of sleeping
> > due to contention, the workload of the CX23418's MPEG encoding engine,
> > and the number of CX23418 devices in the system.
> > 
> > Will all the sleeping that can happen, is the move to a system wq, under
> > cmwq, going to have adverse affects on processing other work items in
> > the system?
> > 
> > I get the feeling it won't be a problem with cmwq, but I haven't paid
> > enough attention to be sure. 
> 
> It won't be a problem.  Now the system_wq supports parallel execution
> of multiple works and manages concurrency automatically.  Work items
> can sleep as necessary without worrying about other work items.

OK, that's what I thought.  I just wanted to ensure that busy CX23418
chips are not going to delay the processing of other work-events in the
rest the system down. 

> ...
> > It is not unusual for scheduled TV recording software to start nearly
> > simultaneous DTV TS, MPEG, and VBI or MPEG Index streams on multiple
> > cards.  So 3 CX23418 cards with 3 streams each.   Let's nominally
> > estimate the timing of the CX18_CPU_DE_SET_MDL commands per stream at
> > the PAL frame rate of 25 Hz; or 1 CX18_CPU_DE_SET_MDL mailbox command
> > per stream per 40 milliseconds.
> 
> IIUC, if they spend any significant amount of time executing, they'll
> be doing so by waiting for events (mutex, IRQ...), right?

Right.  As a CX23418 is expected to do more streaming by the host, the
mailbox mutex contention goes up and the latency of the CX23418
responding to mailbox commands also goes up so there is more wait()ing.


>   If so,
> there's nothing to worry about.  If it's gonna burn a lot of CPU
> cycles, we'll need to use a workqueue marked CPU_INTENSIVE but I don't
> think that's the case here.

Correct, CPU is not the concern here.


> Thank you.

Thanks.  I'll do a proper inspection of the patch tonight.  It looked OK
on cursory review.

Regards,
Andy


  reply	other threads:[~2011-01-04 13:20 UTC|newest]

Thread overview: 119+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-03 13:49 [PATCHSET] workqueue: update workqueue users - replace create_workqueue() Tejun Heo
2011-01-03 13:49 ` [PATCH 01/32] arm/omap: use system_wq in mailbox Tejun Heo
2011-01-03 21:35   ` Kanigeri, Hari
2011-01-04  5:24     ` Tejun Heo
2011-01-25 13:47       ` Tejun Heo
2011-01-25 15:34         ` Hari Kanigeri
2011-01-25 15:34           ` Hari Kanigeri
2011-01-25 15:37           ` Tejun Heo
2011-01-03 13:49 ` [PATCH 02/32] powerpc/cell: use system_wq in cpufreq_spudemand Tejun Heo
2011-01-03 13:49   ` Tejun Heo
2011-01-03 13:49 ` [PATCH 03/32] block: make kblockd_workqueue smarter Tejun Heo
2011-01-03 14:00   ` Jens Axboe
2011-01-03 13:49 ` [PATCH 04/32] bio-integrity: mark kintegrityd_wq highpri and CPU intensive Tejun Heo
2011-01-03 13:49 ` [PATCH 05/32] crypto: mark crypto workqueues CPU_INTENSIVE Tejun Heo
2011-01-03 13:49   ` Tejun Heo
2011-01-04  4:38   ` Herbert Xu
2011-01-04  4:38     ` Herbert Xu
2011-01-03 13:49 ` [PATCH 06/32] acpi: kacpi*_wq don't need WQ_MEM_RECLAIM Tejun Heo
2011-01-03 13:49 ` [PATCH 07/32] cpufreq: use system_wq instead of dedicated workqueues Tejun Heo
2011-01-03 13:49 ` [PATCH 08/32] drm/nouveau: use system_wq instead of dev_priv->wq Tejun Heo
2011-01-03 13:49   ` Tejun Heo
2011-01-05  1:07   ` Ben Skeggs
2011-01-05  1:16     ` Ben Skeggs
2011-01-06 17:29       ` Tejun Heo
2011-01-26 16:49         ` [PATCH UPDATED " Tejun Heo
2011-02-01 10:41           ` Tejun Heo
2011-02-04  1:53             ` Ben Skeggs
2011-02-04 11:03               ` Tejun Heo
2011-01-03 13:49 ` [PATCH 09/32] drm/radeon: " Tejun Heo
2011-01-03 13:49   ` Tejun Heo
2011-01-05  0:21   ` Alex Deucher
2011-01-06  4:31     ` Dave Airlie
2011-01-03 13:49 ` [PATCH 10/32] input/tps6507x-ts: use system_wq instead of dedicated workqueue Tejun Heo
2011-01-03 14:39   ` Dan Carpenter
2011-01-03 16:34     ` Todd Fischer
2011-01-25 14:19       ` Tejun Heo
2011-01-25 16:13         ` Todd Fischer
2011-01-25 16:50           ` Dmitry Torokhov
2011-01-26 10:43             ` Tejun Heo
2011-01-03 13:49 ` [PATCH 11/32] v4l/cx18: update workqueue usage Tejun Heo
2011-01-04  0:54   ` Andy Walls
2011-01-04  8:36     ` Tejun Heo
2011-01-04 13:21       ` Andy Walls [this message]
2011-01-08 17:03   ` Andy Walls
2011-01-03 13:49 ` [PATCH 12/32] i2o: use alloc_workqueue() instead of create_workqueue() Tejun Heo
2011-01-03 13:49 ` [PATCH 13/32] misc/iwmc3200top: use system_wq instead of dedicated workqueues Tejun Heo
2011-01-03 13:49 ` [PATCH 14/32] wireless/ipw2x00: " Tejun Heo
2011-01-06 20:51   ` John W. Linville
2011-01-03 13:49 ` [PATCH 15/32] wireless/libertas[_tf]: " Tejun Heo
2011-02-01 10:52   ` Tejun Heo
2011-01-03 13:49 ` [PATCH 16/32] scsi/be2iscsi,qla2xxx: convert to alloc_workqueue() Tejun Heo
2011-02-01 23:45   ` Mike Christie
2011-02-02 10:25     ` Tejun Heo
2011-02-02 20:41       ` Mike Christie
2011-02-03  9:31         ` Tejun Heo
2011-01-03 13:49 ` [PATCH 17/32] scsi/ibmvstgt: use system_wq instead of vtgtd workqueue Tejun Heo
2011-01-03 17:45   ` Bart Van Assche
2011-01-04  5:20     ` Tejun Heo
2011-01-24 16:09   ` Bart Van Assche
2011-01-24 16:24     ` Tejun Heo
2011-02-01 10:40       ` Tejun Heo
2011-02-01 14:18         ` FUJITA Tomonori
2011-02-01 14:25           ` James Bottomley
2011-02-01 14:29           ` Tejun Heo
2011-01-03 13:49 ` [PATCH 18/32] scsi/scsi_tgt_lib: scsi_tgtd isn't used in memory reclaim path Tejun Heo
2011-01-03 13:49 ` [PATCH 19/32] usb/ueagle-atm: use system_wq instead of dedicated workqueues Tejun Heo
2011-01-03 13:49 ` [PATCH 20/32] video/msm_fb: " Tejun Heo
     [not found]   ` <1294062595-30097-21-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-01-03 17:06     ` Stanislaw Gruszka
2011-01-03 17:06       ` Stanislaw Gruszka
     [not found]       ` <20110103170615.GB2285-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2011-01-03 18:10         ` Daniel Walker
2011-01-03 18:10           ` Daniel Walker
     [not found]           ` <1294078245.18295.5.camel-y5Owza0q8UhBVvN7MMdr1KRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-01-25 13:45             ` Tejun Heo
2011-01-25 13:45               ` Tejun Heo
     [not found]               ` <20110125134558.GY27510-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2011-01-25 18:00                 ` Daniel Walker
2011-01-25 18:00                   ` Daniel Walker
2011-01-25 19:14                   ` David Brown
2011-01-25 19:16                     ` Daniel Walker
     [not found]                       ` <1295982976.25496.29.camel-y5Owza0q8UhBVvN7MMdr1KRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-01-25 22:08                         ` Carl Vanderlip
2011-01-25 22:08                           ` Carl Vanderlip
2011-01-25 23:21   ` David Brown
2011-01-26 10:41     ` Tejun Heo
2011-01-26 18:04       ` David Brown
2011-01-03 13:49 ` [PATCH 21/32] fs/aio: aio_wq isn't used in memory reclaim path Tejun Heo
2011-01-04 15:56   ` Jeff Moyer
2011-01-05 11:28     ` Tejun Heo
2011-01-05 14:50       ` Jeff Moyer
2011-01-05 15:00         ` Benjamin LaHaise
2011-01-05 15:49           ` Jeff Moyer
2011-01-26 11:21   ` [PATCH UPDATED " Tejun Heo
2011-01-26 16:29     ` Jeff Moyer
2011-01-26 16:38       ` Tejun Heo
2011-01-03 13:49 ` [PATCH 22/32] ceph: fsc->*_wq's aren't " Tejun Heo
2011-01-03 17:58   ` Sage Weil
2011-01-03 13:49 ` [PATCH 23/32] net/ceph: make ceph_msgr_wq non-reentrant Tejun Heo
2011-01-03 17:58   ` Sage Weil
2011-01-03 13:49 ` [PATCH 24/32] dlm: dlm workqueues aren't used in memory reclaim path Tejun Heo
2011-01-03 13:58   ` Steven Whitehouse
2011-01-03 13:58     ` [Cluster-devel] " Steven Whitehouse
2011-01-03 14:01     ` Tejun Heo
2011-01-03 14:21       ` Steven Whitehouse
2011-01-03 14:21         ` [Cluster-devel] " Steven Whitehouse
2011-01-03 14:27         ` Tejun Heo
2011-01-03 14:39           ` Steven Whitehouse
2011-01-03 14:39             ` [Cluster-devel] " Steven Whitehouse
2011-01-03 14:44             ` Tejun Heo
2011-01-03 13:49 ` [PATCH 25/32] ext4: convert to alloc_workqueue() Tejun Heo
2011-01-03 13:49 ` [PATCH 26/32] ocfs2: use system_wq instead of ocfs2_quota_wq Tejun Heo
2011-01-03 13:49 ` [PATCH 27/32] reiserfs: make commit_wq use the default concurrency level Tejun Heo
2011-01-03 13:49 ` [PATCH 28/32] xfs: convert to alloc_workqueue() Tejun Heo
2011-01-03 13:49 ` [PATCH 29/32] net/9p: use system_wq instead of p9_mux_wq Tejun Heo
2011-01-03 13:49 ` [PATCH 30/32] net/9p: replace p9_poll_task with a work Tejun Heo
2011-01-03 13:49 ` [PATCH 31/32] rds/ib: use system_wq instead of rds_ib_fmr_wq Tejun Heo
2011-01-03 13:49 ` [PATCH 32/32] rxrpc: rxrpc_workqueue isn't used during memory reclaim Tejun Heo
2011-01-25 14:29 ` [PATCHSET] workqueue: update workqueue users - replace create_workqueue() Tejun Heo
2011-01-25 16:26   ` Dave Jones
2011-01-26 10:40     ` Tejun Heo
2011-01-25 17:47   ` Madhu Iyengar
2011-01-26  4:46   ` Greg KH
2011-02-01 10:44   ` Tejun Heo

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