From: ak@linux.intel.com (Andi Kleen)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: Do not allow unaligned accesses when CONFIG_ALIGNMENT_TRAP
Date: Fri, 27 May 2011 09:53:06 -0700 [thread overview]
Message-ID: <4DDFD6F2.1040304@linux.intel.com> (raw)
In-Reply-To: <1306490709.26257.4.camel@e102144-lin.cambridge.arm.com>
> Do you have any concrete examples of -fconserve-stack giving an overall
> win that isn't in the noise? The fact that the GCC documentation
> explicitly states that enabling the option can lead to `making the
> program slower' does make me question why we're enabling it in the first
> place.
Because the kernel has a limited stack. We had a few cases in the past where
inlining blew it, especially in large ioctl switch() functions which inlined
lots of others.
On modern gccs it's better because it is smarter about sharing stack
slots in large
functions. This was also worked around with manual noinlines.
But it's still far safer to tell gcc to conserve stack.
I consider the ARM gcc behaviour just a bug. The thing was really only
intended
for the inliner (I asked for it originally)
-Andi
next prev parent reply other threads:[~2011-05-27 16:53 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-23 11:16 [PATCH] ARM: Do not allow unaligned accesses when CONFIG_ALIGNMENT_TRAP Catalin Marinas
2011-05-23 12:30 ` Måns Rullgård
2011-05-23 13:25 ` Russell King - ARM Linux
2011-05-23 13:21 ` Russell King - ARM Linux
2011-05-23 13:51 ` Catalin Marinas
2011-05-23 14:37 ` Måns Rullgård
2011-05-23 14:41 ` Catalin Marinas
2011-05-23 14:52 ` Russell King - ARM Linux
2011-05-24 9:39 ` Catalin Marinas
2011-05-24 14:17 ` Måns Rullgård
2011-05-24 15:26 ` Catalin Marinas
2011-05-24 16:23 ` Måns Rullgård
2011-05-24 17:26 ` Nicolas Pitre
2011-05-24 17:13 ` Dave Martin
2011-05-25 11:14 ` Catalin Marinas
2011-05-25 12:43 ` Dave Martin
2011-05-25 13:32 ` Måns Rullgård
2011-05-25 14:05 ` Dave Martin
2011-05-25 14:48 ` Måns Rullgård
2011-05-25 14:50 ` Catalin Marinas
2011-05-25 14:53 ` Måns Rullgård
2011-05-26 17:10 ` Will Deacon
2011-05-26 18:14 ` Måns Rullgård
2011-05-26 19:58 ` Andi Kleen
2011-05-26 21:03 ` Nicolas Pitre
2011-05-26 21:10 ` Andi Kleen
2011-05-26 21:26 ` Måns Rullgård
2011-05-27 10:05 ` Will Deacon
2011-05-27 16:53 ` Andi Kleen [this message]
2011-05-26 21:51 ` Russell King - ARM Linux
2011-05-26 22:29 ` Andi Kleen
2011-05-27 8:38 ` Catalin Marinas
2011-05-27 8:54 ` Russell King - ARM Linux
2011-05-27 9:51 ` Catalin Marinas
2011-05-27 9:56 ` Catalin Marinas
2011-05-27 12:46 ` Måns Rullgård
2011-05-28 15:34 ` [PATCH] Disable -fconserve-stack on ARM Andi Kleen
2011-05-31 16:30 ` Catalin Marinas
2011-05-31 18:01 ` Andi Kleen
2011-06-02 13:08 ` Catalin Marinas
[not found] <mailman.254.1306496353.1533.linux-arm-kernel@lists.infradead.org>
2011-05-27 12:14 ` [PATCH] ARM: Do not allow unaligned accesses when CONFIG_ALIGNMENT_TRAP Frank Hofmann
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