linux-kernel - Re: [RFC PATCH 1/3] Unified trace buffer

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Message-ID: <33307c790809241356l79acc57cxa4fb84c1e5dae1da@mail.gmail.com>
Date:	Wed, 24 Sep 2008 13:56:38 -0700
From:	"Martin Bligh" <mbligh@...gle.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>
Cc:	"Peter Zijlstra" <peterz@...radead.org>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	prasad@...ux.vnet.ibm.com,
	"Mathieu Desnoyers" <compudj@...stal.dyndns.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	"David Wilder" <dwilder@...ibm.com>, hch@....de,
	"Tom Zanussi" <zanussi@...cast.net>,
	"Steven Rostedt" <srostedt@...hat.com>
Subject: Re: [RFC PATCH 1/3] Unified trace buffer

> On Wed, 24 Sep 2008, Martin Bligh wrote:
>>
>> If we use 32 bits instead of 27, then the timestamp events are only
>> about once per second, which is probably fine for overhead ... ?
>
> You'd have them ONCE IN A BLUE MOON.
>
> If there is nothing going on, you don't need the timestamps at all.

Yeah, you're right - we can just mark it dirty, and 'pre-log' the timestamp
events when someone calls a reserve and we haven't logged anything
for more time than we can store. Did not think of that. Was only 5 bits
for us, not an extra 37, but still, is much better.

Is a 5-bit event id generic enough though?
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