linux-kernel - Re: [PATCH 3/2] perf tools: Use DECLARE_BITMAP instead of an open-coded array

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Message-ID: <20091017160338.GA10344@nowhere>
Date:	Sat, 17 Oct 2009 18:03:41 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 3/2] perf tools: Use DECLARE_BITMAP instead of an
	open-coded array

On Sat, Oct 17, 2009 at 05:57:18PM +0200, Frederic Weisbecker wrote:
> Use DECLARE_BITMAP instead of an open coded array for our bitmap
> of featured sections.
> 
> This makes the array an unsigned long instead of a u64 but since
> we use a 256 bits bitmap, the array size shouldn't vary between
> different boxes.


That said I would really feel more comfortable if someone can
confirm that.



> @@ -143,12 +141,12 @@ struct perf_file_header {
>  	struct perf_file_section	attrs;
>  	struct perf_file_section	data;
>  	struct perf_file_section	event_types;
> -	feat_mask_t			adds_features;
> +	DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);


I think having adds_features as an unsigned long won't
hurt because we have HEAD_FEAT_BITS % 64 == 0

It would certainly hurt if we had, say, HEAD_FEAT_BITS = 257

But may be I forget a corner case. I hope someone can double
check that. Thanks.

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