* IRQ dynamic distribution : A9-MPCore + GIC
@ 2010-08-03 4:06 Suresh Shukla
2010-08-03 7:32 ` Russell King - ARM Linux
0 siblings, 1 reply; 2+ messages in thread
From: Suresh Shukla @ 2010-08-03 4:06 UTC (permalink / raw)
To: linux-arm-kernel
Hi,
Is there any available work on IRQ dynamic distribution for A9-MPCore
platform with GIC ?
I see it is available for x86 APIC platform and priority based support
can be implemented for A9-MPCore/GIC combination.
It would be useful for reducing latency.
thanks,
Suresh
^ permalink raw reply [flat|nested] 2+ messages in thread
* IRQ dynamic distribution : A9-MPCore + GIC
2010-08-03 4:06 IRQ dynamic distribution : A9-MPCore + GIC Suresh Shukla
@ 2010-08-03 7:32 ` Russell King - ARM Linux
0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2010-08-03 7:32 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Aug 03, 2010 at 09:36:32AM +0530, Suresh Shukla wrote:
> Hi,
>
> Is there any available work on IRQ dynamic distribution for A9-MPCore
> platform with GIC ?
> I see it is available for x86 APIC platform and priority based support
> can be implemented for A9-MPCore/GIC combination.
I tried to get IRQ balancing working with the initial ARM SMP
implementation but I found it impossible to behave sanely within
kernel space. I don't remember what the exact problems were though -
this was five or so years ago.
The advice I got from Arjan van de Ven (author of Powertop) was
not to bother - the kernel IRQ balancer is flawed because it constantly
shifts IRQs between CPUs, meaning that they don't benefit from cache
hotness. There are also implementations for IRQ balancing in userspace
which could do a far better job.
^ permalink raw reply [flat|nested] 2+ messages in thread
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