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

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Message-ID: <Pine.LNX.4.58.0706281146460.22479@gandalf.stny.rr.com>
Date:	Thu, 28 Jun 2007 11:54:35 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Alexey Kuznetsov <kuznet@....inr.ac.ru>
cc:	Ingo Molnar <mingo@...e.hu>, Jeff Garzik <jeff@...zik.org>,
	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


On Thu, 28 Jun 2007, Alexey Kuznetsov wrote:
> > the context-switch argument i'll believe if i see numbers. You'll
> > probably need in excess of tens of thousands of irqs/sec to even be able
> > to measure its overhead. (workqueues are driven by nice kernel threads
> > so there's no TLB overhead, etc.)
>
> It was authors of the patch who were supposed to give some numbers,
> at least one or two, just to prove the concept. :-)

The problem is that we don't have the hardware that uses tasklets in
critical ways. My original patch series had a debug print in every
function (tasklet_schedule and friends).   I got a few scattered prints on
all my boxes but no flooding of prints. So I can't show that this will
hurt, because on my boxes it does not.

>
> You could set realtime prioriry by default, not a poor nice -5.
> If some network adapters were killed just because I run some task
> with nice --22, it would be just ridiculous.

This is my fault to the patch series. I compelety forgot to up the prio.
My next series will include a change where the tasklet work queue will run
at something like prio FIFO 98 (or maybe 99?)

This is a bit embarrassing that I forgot to do this, since I'm a
real-time developer ;-)

-- Steve

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