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SubjectRe: [PATCH] Re: Bad network performance over 2Gbps
Hi!

> [X86] IRQBALANCE: Mark as BROKEN and disable by default
>
> The IRQBALANCE option causes interrupts to bounce all around on SMP systems
> quickly burying the CPU in migration cost and cache misses. Mainly affected are
> network interrupts and this results in one CPU pegged in softirqd completely.
>
> Disable this option and provide documentation to a better solution (userspace
> irqbalance daemon does overall the best job to begin with and only manual setting
> of smp_affinity will beat it).
>
> Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
>
> ---
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 6c70fed..956aa22 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1026,13 +1026,17 @@ config EFI
> platforms.
>
> config IRQBALANCE
> - def_bool y
> + def_bool n

ACK.
> prompt "Enable kernel irq balancing"
> - depends on X86_32 && SMP && X86_IO_APIC
> + depends on X86_32 && SMP && X86_IO_APIC && BROKEN

This is wrong. irqbalance works, there's nothing wrong with it; but it
has nasty sideffects.

> help
> The default yes will allow the kernel to do irq load balancing.
> Saying no will keep the kernel from doing irq load balancing.
>
> + This option is known to cause performance issues on SMP
> + systems. The preferred method is to use the userspace
> + 'irqbalance' daemon instead. See http://irqbalance.org/.
> +

ACK.

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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