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SubjectRe: [PATCH] irq: Add node_affinity CPU masks for smarter irqbalance hints
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On Mon, 2009-11-23 at 22:17 -0700, Yong Zhang wrote:
> [snip]
> >>
> >> 1) I think you should consider CONFIG_CPUMASK_OFFSTACK which will affect
> >> node_affinity.
> >> 2) It seems like this patch can't work with SPARSE_IRQ.
> >
> > This mechanism isn't going to be used by any internal kernel mechanism
> > for determining interrupt placement or operation. It's purely something
> > that either a driver can modify, or external script (through /proc),
> > that irqbalance will make use of. If irqbalance isn't running, or the
> > current version of irqbalance doesn't support reading node_affinity,
> > then it won't affect the system's operation.
> >
> > If irqbalance does support it, it'll read whatever the supplied mask is,
> > and then will try and balance interrupts within that mask. It will bail
> > if the mask is invalid, or won't apply to the running system, just like
> > how putting a bogus mask into smp_affinity is ignored.
> >
> > If there's something I'm missing beyond this with the two suggestions
> > you've made (I looked into those two parameters and tried to draw
> > conclusions), please let me know.
>
> My two suggestions are both about your adding node_affinity. Before you can
> use this element, you must initialise it firstly. You can refer how
> irq_desc::affinity
> is used in function alloc_desc_masks().
> include/linux/irq.h:
> static inline bool alloc_desc_masks(struct irq_desc *desc, int node,
> bool boot)
> {
> gfp_t gfp = GFP_ATOMIC;
>
> if (boot)
> gfp = GFP_NOWAIT;
>
> #ifdef CONFIG_CPUMASK_OFFSTACK
> if (!alloc_cpumask_var_node(&desc->affinity, gfp, node))
> return false;
>
> #ifdef CONFIG_GENERIC_PENDING_IRQ
> if (!alloc_cpumask_var_node(&desc->pending_mask, gfp, node)) {
> free_cpumask_var(desc->affinity);
> return false;
> }
> #endif
> #endif
> return true;
> }
>

Ah, ok. I see what you were referring to now. Let me respin the patch
and send a second version.

Thanks Yong,

-PJ Waskiewicz



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