linux-kernel - Re: [RFC PATCH 0/6] Convert all tasklets to workqueues

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Date:	Fri, 29 Jun 2007 10:24:53 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Christoph Hellwig <hch@...radead.org>,
	john stultz <johnstul@...ibm.com>,
	Oleg Nesterov <oleg@...sign.ru>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>, matthew.wilcox@...com
Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues

Steven Rostedt wrote:
> I had very little hope for this magic switch to get into mainline. (maybe
> get it into -mm)  But the thing was is that tasklets IMHO are over used.
> As Ingo said, there are probably only 2 or 3 places in the kernel that a
> a switch to work queue conversion couldn't solve.

This is purely a guess, backed by zero evidence.

These network drivers were hand-tuned to use tasklets.  Sure it will 
WORK as a workqueue, but that says nothing equivalence.


> Those places could then
> probably be solved by a different design (yes that would take work).

Network driver patches welcome :)


> Tasklets are there because there
> wasn't work queues or kthreads at the time of solving the solution that
> tasklets solved.

Completely false, at least in network driver land.  Threads existed and 
were used (proof: 8139too, among others).

Kernel threads were not used for hot path network packet shovelling 
because they were too damn slow.  Tasklets were single-threaded, fast, 
simple and immediate.  Workqueues today are simple and almost-fast.

	Jeff


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