* [PATCH] UV: cpu_relax in uv_wait_completion
@ 2009-01-15 15:51 Cliff Wickman
2009-01-15 17:57 ` Ingo Molnar
0 siblings, 1 reply; 2+ messages in thread
From: Cliff Wickman @ 2009-01-15 15:51 UTC (permalink / raw)
To: linux-kernel; +Cc: mingo
From: Cliff Wickman <cpw@sgi.com>
The function uv_wait_completion() spins on reads of a memory-mapped
register, waiting for completion of BAU hardware replies.
It should call "cpu_relax()" between those reads to improve performance
on hyperthreaded configurations.
Signed-off-by: Cliff Wickman <cpw@sgi.com>
Acked-by: Jack Steiner <steiner@sgi.org>
---
arch/x86/kernel/tlb_uv.c | 1 +
1 file changed, 1 insertion(+)
Index: linux/arch/x86/kernel/tlb_uv.c
===================================================================
--- linux.orig/arch/x86/kernel/tlb_uv.c
+++ linux/arch/x86/kernel/tlb_uv.c
@@ -200,6 +200,7 @@ static int uv_wait_completion(struct bau
destination_timeouts = 0;
}
}
+ cpu_relax();
}
return FLUSH_COMPLETE;
}
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] UV: cpu_relax in uv_wait_completion
2009-01-15 15:51 [PATCH] UV: cpu_relax in uv_wait_completion Cliff Wickman
@ 2009-01-15 17:57 ` Ingo Molnar
0 siblings, 0 replies; 2+ messages in thread
From: Ingo Molnar @ 2009-01-15 17:57 UTC (permalink / raw)
To: Cliff Wickman; +Cc: linux-kernel
* Cliff Wickman <cpw@sgi.com> wrote:
>
> From: Cliff Wickman <cpw@sgi.com>
>
> The function uv_wait_completion() spins on reads of a memory-mapped
> register, waiting for completion of BAU hardware replies.
> It should call "cpu_relax()" between those reads to improve performance
> on hyperthreaded configurations.
>
> Signed-off-by: Cliff Wickman <cpw@sgi.com>
> Acked-by: Jack Steiner <steiner@sgi.org>
>
> ---
> arch/x86/kernel/tlb_uv.c | 1 +
> 1 file changed, 1 insertion(+)
applied to tip/x86/urgent, thanks Cliff!
Ingo
^ permalink raw reply [flat|nested] 2+ messages in thread
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2009-01-15 15:51 [PATCH] UV: cpu_relax in uv_wait_completion Cliff Wickman
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