linux-kernel - Re: [patch] sched: make cpu_clock() not use the rq clock

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Message-Id: <1185504973.6609.25.camel@perkele>
Date:	Thu, 26 Jul 2007 22:56:13 -0400
From:	Eric St-Laurent <ericstl34@...patico.ca>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] sched: make cpu_clock() not use the rq clock

On Thu, 2007-26-07 at 11:00 +0200, Ingo Molnar wrote:
> Subject: sched: make cpu_clock() not use the rq clock
> From: Ingo Molnar <mingo@...e.hu>
> 
> it is enough to disable interrupts to get the precise rq-clock
> of the local CPU.

Hi Ingo,

Those new fast nanoseconds resolution clock APIs are nice but it seems
to me that their naming and _where_ they are implemented in the tree is
a little odd, IMO.

We have:

1. sched_clock() is in kernel/sched.c (weak implementation)
2. sched_clock() is in arch/i386/kernel/tsc.c (architecture override)
3. rq_clock() is in kernel/sched.c
4. cpu_clock() is in kernel/sched.c

I would suggest:

1. rename sched_clock() (remove sched_ as it's not sched specific
anymore) and place it in kernel/time/...
2. rename the architecture specific version of it too 

This first function is the basic fast ns clock

3. base your rq_clock() on cpu_clock() (#4) or use the later directly.

This is local to sched.c

4. move cpu_clock() in kernel/time/...

This the per-cpu monotonic version.

See my point? Base the scheduler clock from a general kernel API, not
the other way around.

Just a suggestion.

Best regards,

- Eric

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