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From: Nick Piggin <>
To: Linus Torvalds <>
Cc: john stultz <>,
	Joel Becker <>,
	lkml <>,
	Marcelo Tosatti <>
Subject: Re: get_cycles() on i386
Date: Wed, 05 Nov 2003 13:53:57 +1100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Linus Torvalds wrote:

>On 4 Nov 2003, john stultz wrote:
>>CONFIG_X86_TSC be the devil. Personally, I'd much prefer dropping the
>>compile time option and using dynamic detection. Something like (not
>>recently tested and i believe against 2.5.something, but you get the
>Some of the users are really timing-critical (eg scheduler).

The scheduler uses its own sched_clock which only gives jiffies
resolution if CONFIG_NUMA is defined. Unfortunate because I think
its interactive behaviour isn't so good with ms resolution.

The scheduler does not need to have synchronised TSCs though, I think.
It just means 2 more calls to sched_clock in a slow path (smp migration).

  reply	other threads:[~2003-11-05  2:57 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-11-04 23:22 Joel Becker
2003-11-04 23:27 ` john stultz
2003-11-04 23:54   ` Linus Torvalds
2003-11-05  2:53     ` Nick Piggin [this message]
2003-11-05  3:02       ` Nick Piggin
2003-11-05 13:35     ` Marcelo Tosatti
2003-12-05 15:55   ` Marcelo Tosatti

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