From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Joakim Tjernlund <joakim.tjernlund@transmode.se>,
Eric Dumazet <eric.dumazet@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: slow nanosleep?
Date: Wed, 08 Sep 2010 15:00:18 +0200 [thread overview]
Message-ID: <1283950818.23762.20.camel@laptop> (raw)
In-Reply-To: <alpine.LFD.2.00.1009081442390.2477@localhost6.localdomain6>
On Wed, 2010-09-08 at 14:43 +0200, Thomas Gleixner wrote:
> > However nanosleep with 1 ns and prctl(PR_SET_TIMERSLACK, 1) takes
> > about 8 us on x86(Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz)
> > and 20 us on my slower ppc board. Is that system call overhead
> > or possibly some error?
>
> That's overhead I fear. We go way up to enqueue/arm the timer until we
> figure out that the timeout already happened.
Well, there's also the fact that his ppc board is simply dead slow,
using the freq ratio: 3166/266 you'd expect (at a similar ins/clock
ratio) the ppc to take 95us.
So in fact the pcc taking 20us is actually quite good.
next prev parent reply other threads:[~2010-09-08 13:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-08 7:45 slow nanosleep? Joakim Tjernlund
2010-09-08 7:56 ` Eric Dumazet
2010-09-08 8:04 ` Joakim Tjernlund
2010-09-08 8:24 ` Eric Dumazet
2010-09-08 9:12 ` Joakim Tjernlund
2010-09-08 9:51 ` Thomas Gleixner
2010-09-08 10:14 ` Eric Dumazet
2010-09-08 10:17 ` Thomas Gleixner
2010-09-08 12:11 ` Joakim Tjernlund
2010-09-08 12:43 ` Thomas Gleixner
2010-09-08 13:00 ` Peter Zijlstra [this message]
2010-09-08 13:44 ` Joakim Tjernlund
2010-09-08 13:51 ` Peter Zijlstra
2010-09-08 13:52 ` Thomas Gleixner
2010-09-08 14:19 ` Joakim Tjernlund
2010-09-08 14:30 ` Thomas Gleixner
2010-09-08 14:33 ` Joakim Tjernlund
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