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Message-ID: <20090423044228.GA2428@ucw.cz> Date: Thu, 23 Apr 2009 06:42:29 +0200 From: Pavel Machek <pavel@....cz> To: Peter Zijlstra <peterz@...radead.org> Cc: Christoph Lameter <cl@...ux.com>, Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: Re: Scheduler regression: Too frequent timer interrupts(?) On Fri 2009-04-17 17:28:57, Peter Zijlstra wrote: > On Fri, 2009-04-17 at 11:04 -0400, Christoph Lameter wrote: > > On Fri, 17 Apr 2009, Peter Zijlstra wrote: > > > > > And a random 1us cutoff, is well, random. > > > > Its got to be somewhere. > > No it doesn't, a cutoff is useless. If I steal cputime at units below > the cutoff I can, in the limit, steal up to 100% cpu time and you'd not > notice. Are you sure cutoff is useless? Irq entry/exit is sure to take > 1usec, right? > > > So 5 <1us interruption are not at all accounted, whereas a single 1>us > > > interruption is. I'd rather get rid of those 5 than try and shave a bit > > > of the one, if you get what I mean. > > > > Ok. We can set the threshold lower and see how that goes. > > Pointless. See above. I'd say that taking interrupt and returning in below 1000nsec is impossible, even on very fast hw. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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