linux-kernel - Re: [PATCH] perf: use default compiler mode by default

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Date:	Mon, 23 Nov 2009 22:14:41 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: use default compiler mode by default

Ingo Molnar writes:

> I'd still like to hear back from Paulus whether PowerPC is affected 
> negatively - IIRC it was PowerPC where we got the -m64 from originally.

It seems that a 32-bit perf now works on a 64-bit kernel on powerpc,
so I don't have any hard objection to this patch.  (For some reason,
perf top isn't getting any samples, so I'll have to chase that.)

Many distros on powerpc default to 32-bit userspace on 64-bit
machines, since that has a slight performance and size benefit for
most programs.  I expect perf is better as a 64-bit binary, since it
does a lot of 64-bit arithmetic, so users of those distros on 64-bit
machines would need to do "make EXTRA_CFLAGS=-m64".

Paul.
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