From: Jeremy Fitzhardinge <jeremy@goop.org>
To: John Richard Moser <nigelenki@comcast.net>
Cc: Chris Friesen <cfriesen@nortel.com>, linux-kernel@vger.kernel.org
Subject: Re: Can context switches be faster?
Date: Thu, 12 Oct 2006 13:35:12 -0700 [thread overview]
Message-ID: <452EA700.9060009@goop.org> (raw)
In-Reply-To: <452EA441.6070703@comcast.net>
John Richard Moser wrote:
> That's a load more descriptive :D
>
> 0.890 uS, 0.556uS/cycle, that's barely 2 cycles you know. (Pentium M)
> PPC performs similarly, 1 cycle should be about 1uS.
>
No, you're a factor of 1000 off - these numbers show the context switch
is around 1600-75000 cycles. And that doesn't really tell the whole
story: if caches/TLB get flushed on context switch, then the newly
switched-to task will bear the cost of having cold caches, which isn't
visible in the raw context switch time.
But modern x86 processors have a very quick context switch time, and I
don't think there's much room for improvement aside from
micro-optimisations (though that might change if the architecture grows
a way to avoid flushing the TLB on switch).
J
next prev parent reply other threads:[~2006-10-12 20:33 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-12 15:44 Can context switches be faster? John Richard Moser
2006-10-12 15:53 ` John Richard Moser
2006-10-12 17:19 ` Russell King
2006-10-12 18:25 ` John Richard Moser
2006-10-12 18:37 ` Arjan van de Ven
2006-10-12 18:56 ` John Richard Moser
2006-10-12 19:02 ` Arjan van de Ven
2006-10-13 11:05 ` James Courtier-Dutton
2006-10-13 14:51 ` Chase Venters
2006-10-12 18:20 ` Phillip Susi
2006-10-12 18:29 ` John Richard Moser
2006-10-13 2:53 ` Andrew James Wade
2006-10-13 5:29 ` John Richard Moser
2006-10-13 16:56 ` Andrew James Wade
2006-10-13 17:24 ` John Richard Moser
2006-10-12 19:57 ` Chris Friesen
2006-10-12 20:23 ` John Richard Moser
2006-10-12 20:29 ` Arjan van de Ven
2006-10-12 20:36 ` John Richard Moser
2006-10-12 20:35 ` Jeremy Fitzhardinge [this message]
2006-10-13 23:32 ` Andreas Mohr
2006-10-13 23:47 ` David Lang
2006-10-14 0:14 ` Jeremy Fitzhardinge
2006-10-14 0:30 ` Alan Cox
2006-10-14 0:14 ` Jeremy Fitzhardinge
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