From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@osdl.org>,
Zwane Mwaikambo <zwane@fsmlabs.com>,
linux-kernel@vger.kernel.org, wli@holomorphy.com
Subject: Re: [PATCH] remove LOCK_SECTION from x86_64 spin_lock asm
Date: Thu, 16 Sep 2004 08:58:05 +0200 [thread overview]
Message-ID: <20040916065805.GA12244@elte.hu> (raw)
In-Reply-To: <20040916065342.GE12915@wotan.suse.de>
* Andi Kleen <ak@suse.de> wrote:
> > the alternative would be to unwind the stack - quite some task on some
> > platforms ...
>
> Sometimes call graph profiling would be very useful, but I wouldn't
> want the profiler to do it by default, especially not for this silly
> simple case. dwarf2 unwinding is complex enough that just requiring
> frame pointers for the CG case would look attractive.
but ... frame pointers are overhead to all of the kernel. (the overhead
is less pronounced on architectures with more registers, but even with
15 registers, 14 or 15 can still be a difference.) While unwinding is
overhead to profiling only - if enabled. Also, there could be other
functionality (exception handling?) that could benefit from dwarf2
unwinding.
Ingo
next prev parent reply other threads:[~2004-09-16 6:56 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-15 16:01 [PATCH] remove LOCK_SECTION from x86_64 spin_lock asm Zwane Mwaikambo
2004-09-15 21:45 ` Andrew Morton
2004-09-15 17:55 ` Zwane Mwaikambo
2004-09-15 21:47 ` Ingo Molnar
2004-09-16 6:13 ` Andi Kleen
2004-09-16 6:27 ` Ingo Molnar
2004-09-16 6:44 ` Andi Kleen
2004-09-16 6:51 ` Ingo Molnar
2004-09-16 6:53 ` Andi Kleen
2004-09-16 6:58 ` Ingo Molnar [this message]
2004-09-16 7:09 ` Andi Kleen
2004-09-16 7:19 ` Ingo Molnar
2004-09-16 7:29 ` Andi Kleen
2004-09-16 7:44 ` Ingo Molnar
2004-09-16 7:53 ` Andi Kleen
2004-09-16 9:01 ` Andi Kleen
2004-09-16 12:44 ` Zwane Mwaikambo
2004-09-16 19:30 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2004-09-15 22:42 Andrew Chew
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