linux-kernel - Re: [PATCHSET] workqueue: concurrency managed workqueue, take#4

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Date:	Sun, 28 Feb 2010 12:11:23 +1100
From:	Anton Blanchard <anton@...ba.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	torvalds@...ux-foundation.org, mingo@...e.hu, peterz@...radead.org,
	awalls@...ix.net, linux-kernel@...r.kernel.org, jeff@...zik.org,
	akpm@...ux-foundation.org, jens.axboe@...cle.com,
	rusty@...tcorp.com.au, cl@...ux-foundation.org,
	dhowells@...hat.com, arjan@...ux.intel.com, avi@...hat.com,
	johannes@...solutions.net, andi@...stfloor.org, oleg@...hat.com
Subject: Re: [PATCHSET] workqueue: concurrency managed workqueue, take#4


Hi Tejun,

I gave the workqueue patches a spin on PowerPC. I'm particularly interested
from an OS jitter perspective, and that these patches wont introduce more
jitter.  It looks like we reach a steady state of worker threads and arent
continually creating and destroying them which is good. This could be a big
deal on compute CPUs (CPUs isolated via isol_cpus or cpusets).

A few things I've found so far:

1. NR_CPUS > 32 causes issues with the workqueue debugfs code:

kernel/workqueue.c:3314: warning: left shift count >= width of type
kernel/workqueue.c:3323: warning: left shift count >= width of type
kernel/workqueue.c:3323: warning: integer overflow in expression
kernel/workqueue.c:3324: warning: enumeration values exceed range of largest integer
kernel/workqueue.c: In function ‘wq_debugfs_decode_pos’:
kernel/workqueue.c:3336: warning: right shift count is negative
kernel/workqueue.c:3337: warning: right shift count is negative
kernel/workqueue.c: In function ‘wq_debugfs_next_pos’:
kernel/workqueue.c:3435: warning: left shift count is negative
kernel/workqueue.c:3436: warning: left shift count is negative
kernel/workqueue.c: In function ‘wq_debugfs_start’:
kernel/workqueue.c:3455: warning: left shift count >= width of type

2. cifs needs to be converted:

fs/cifs/cifsfs.c: In function ‘exit_cifs’:
fs/cifs/cifsfs.c:1067: error: ‘system_single_wq’ undeclared (first use in this function)
fs/cifs/cifsfs.c:1067: error: (Each undeclared identifier is reported only once
fs/cifs/cifsfs.c:1067: error: for each function it appears in.)

Anton
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