From: robherring2@gmail.com (Rob Herring)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: lib: use LDRD/STRD for data copy
Date: Mon, 19 Mar 2012 11:36:53 -0500 [thread overview]
Message-ID: <4F6760A5.9040506@gmail.com> (raw)
In-Reply-To: <20120319154123.GP15988@n2100.arm.linux.org.uk>
On 03/19/2012 10:41 AM, Russell King - ARM Linux wrote:
> On Mon, Mar 19, 2012 at 09:36:41AM -0500, Rob Herring wrote:
>> On 03/19/2012 03:55 AM, Russell King - ARM Linux wrote:
>>> On Mon, Mar 19, 2012 at 04:02:48PM +0900, Boojin Kim wrote:
>>>> This patch uses LDRD/STRD that loads and stores data as DWORD unit
>>>> for the copy of 8-words data.
>>>> It brings better performance than LDRM/STRM that was used originally.
>>>
>>> And what about CPUs that don't have ldrd/strd ?
>>>
>>
>> And what about CPUs that do have ldrd/strd but is slower than ldm/stm?
>> I'm pretty sure that is almost everything currently out there.
>
> The double-word load/stores were introduced in ARMv6. Some Intel based
> CPUs prior to this have the support as well. Everything else doesn't.
>
> So taht's nowhere close to 'almost everything'.
I meant of all platforms that support both instructions, ldm/stm will be
faster than ldrd/strd on almost all of them AFAIK. I don't think the
claim about being faster is true for an CortexA9 or anything prior.
Linaro folks have done some benchmarking in this area and would be
better to comment.
Rob
next prev parent reply other threads:[~2012-03-19 16:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-19 7:02 [PATCH] ARM: lib: use LDRD/STRD for data copy Boojin Kim
2012-03-19 8:55 ` Russell King - ARM Linux
2012-03-19 14:36 ` Rob Herring
2012-03-19 15:41 ` Russell King - ARM Linux
2012-03-19 16:34 ` Måns Rullgård
2012-03-19 16:36 ` Rob Herring [this message]
2012-03-19 16:53 ` Nicolas Pitre
2012-03-19 17:11 ` Måns Rullgård
2012-03-19 20:11 ` Michael Hope
2012-03-20 0:21 ` Boojin Kim
2012-03-19 14:10 ` Nicolas Pitre
2012-03-20 0:05 ` Boojin Kim
2012-03-27 0:26 ` [PATCH 1/2] ARM: lib: Add optimized memcpy with 64 byte pld size Boojin Kim
2012-03-27 2:35 ` Nicolas Pitre
2012-03-28 0:28 ` Boojin Kim
2012-03-28 5:23 ` Nicolas Pitre
2012-03-29 4:00 ` [PATCH 0/4] memcpy optimized with strd/ldrd Nicolas Pitre
2012-03-29 4:00 ` [PATCH 1/4] ARM: copy_template.S: move some registers around Nicolas Pitre
2012-03-29 4:00 ` [PATCH 2/4] ARM: copy_template.S: rework the unaligned copy loop Nicolas Pitre
2012-03-29 4:00 ` [PATCH 3/4] ARM: copy_template.S: enforce contigous register set with memory accessors Nicolas Pitre
2012-03-29 4:00 ` [PATCH 4/4] ARM: option to select LDRD/STRD optimized memory copy Nicolas Pitre
2012-03-27 0:27 ` [PATCH 2/2] ARM: lib: use LDRD/STRD for data copy Boojin Kim
2012-03-27 7:40 ` Russell King - ARM Linux
2012-03-28 0:19 ` Boojin Kim
2012-03-28 4:10 ` Boojin Kim
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