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SubjectRe: [PATCH] Re: Bad network performance over 2Gbps
Pavel Machek wrote:
> 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.

ok, I'm fine with taking that part out of the patch.

Ingo, want me to send an updated patch?


>
>> 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.
>



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