linux-kernel - Re: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable & enable from context tracking on syscall entry

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Date:	Fri, 01 May 2015 12:40:30 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, williams@...hat.com,
	Andrew Lutomirski <luto@...nel.org>, fweisbec@...hat.com,
	Peter Zijlstra <peterz@...radead.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable
 & enable from context tracking on syscall entry

On 05/01/2015 12:37 PM, Ingo Molnar wrote:

> Also note that this bit in context_tracking_enter():
> 
>                         if (state == CONTEXT_USER) {
>                                 trace_user_enter(0);
>                                 vtime_user_enter(current);
>                         }
> 
> 
> is related to precise time measurement of user/kernel execution times, 
> it's not needed by the scheduler at all, it's just exported to 
> tooling. It's not fundamental to the scheduler.

Any objections to the idea from the other thread to simply keep
the time accumulating in buffers in local_clock() units, and
only update the task vtime once a second or so?

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