* Question about r4k_clear_page_xxx()
@ 2002-04-10 2:14 Rani Assaf
2002-04-10 11:10 ` Florian Lohoff
2002-04-12 5:04 ` Ralf Baechle
0 siblings, 2 replies; 3+ messages in thread
From: Rani Assaf @ 2002-04-10 2:14 UTC (permalink / raw)
To: linux-mips
Hi,
I was cleaning duplicate code between my port of IDT RC32355 and the
current tree. I want to use r4k_clear_page_d16() but the function uses
store double (sd) which is not available on this processor.
What's the reason for having r4k_clear_page_xxx() use store double and
not r4k_copy_page_xxx()??
Regards,
Rani
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Question about r4k_clear_page_xxx()
2002-04-10 2:14 Question about r4k_clear_page_xxx() Rani Assaf
@ 2002-04-10 11:10 ` Florian Lohoff
2002-04-12 5:04 ` Ralf Baechle
1 sibling, 0 replies; 3+ messages in thread
From: Florian Lohoff @ 2002-04-10 11:10 UTC (permalink / raw)
To: Rani Assaf; +Cc: linux-mips
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On Wed, Apr 10, 2002 at 04:14:08AM +0200, Rani Assaf wrote:
> Hi,
>
> I was cleaning duplicate code between my port of IDT RC32355 and the
> current tree. I want to use r4k_clear_page_d16() but the function uses
> store double (sd) which is not available on this processor.
>
> What's the reason for having r4k_clear_page_xxx() use store double and
> not r4k_copy_page_xxx()??
Just from my guess - r4k_copy_page will pollute the d-cache with the
empty page you are reading. You have twice as much instruction (load +
store) which effectively will give you half the performance.
If "sd" is not available you might want to implement your clear_page
with sw zero, x(a0) like the sd version.
Flo
--
Florian Lohoff flo@rfc822.org +49-5201-669912
Nine nineth on september the 9th Welcome to the new billenium
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Question about r4k_clear_page_xxx()
2002-04-10 2:14 Question about r4k_clear_page_xxx() Rani Assaf
2002-04-10 11:10 ` Florian Lohoff
@ 2002-04-12 5:04 ` Ralf Baechle
1 sibling, 0 replies; 3+ messages in thread
From: Ralf Baechle @ 2002-04-12 5:04 UTC (permalink / raw)
To: Rani Assaf; +Cc: linux-mips
On Wed, Apr 10, 2002 at 04:14:08AM +0200, Rani Assaf wrote:
> I was cleaning duplicate code between my port of IDT RC32355 and the
> current tree. I want to use r4k_clear_page_d16() but the function uses
> store double (sd) which is not available on this processor.
>
> What's the reason for having r4k_clear_page_xxx() use store double and
> not r4k_copy_page_xxx()??
The 32-bit kernel doesn't save or restore the upper 32-bits of general
purpose registers. Therefore 64-bit stores can only be used with the
$zero register.
Ralf
^ permalink raw reply [flat|nested] 3+ messages in thread
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2002-04-10 2:14 Question about r4k_clear_page_xxx() Rani Assaf
2002-04-10 11:10 ` Florian Lohoff
2002-04-12 5:04 ` Ralf Baechle
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