Messages in this thread |  | | | Date | Tue, 24 Nov 2009 23:23:44 +0100 (CET) | | From | Thomas Gleixner <> | | Subject | Re: [PATCH v2] irq: Add node_affinity CPU masks for smarter irqbalance hints |
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On Tue, 24 Nov 2009, Peter P Waskiewicz Jr wrote: > On Tue, 2009-11-24 at 13:56 -0800, Thomas Gleixner wrote: > > On Tue, 24 Nov 2009, David Miller wrote: > > > > > From: Thomas Gleixner <tglx@linutronix.de> > > > Date: Tue, 24 Nov 2009 12:07:35 +0100 (CET) > > > > > > > And what does the kernel do with this information and why are we not > > > > using the existing device/numa_node information ? > > > > > > It's a different problem space Thomas. > > > > > > If the device lives on NUMA node X, we still end up wanting to > > > allocate memory resources (RX ring buffers) on other NUMA nodes on a > > > per-queue basis. > > > > > > Otherwise a network card's forwarding performance is limited by the > > > memory bandwidth of a single NUMA node, and on a multiqueue cards we > > > therefore fare much better by allocating each device RX queue's memory > > > resources on a different NUMA node. > > > > > > It is this NUMA usage that PJ is trying to export somehow to userspace > > > so that irqbalanced and friends can choose the IRQ cpu masks more > > > intelligently. > > > > So you need a preferred irq mask information on a per IRQ basis and > > that mask is not restricted to the CPUs of a single NUMA node, right ? > > > Just to clarify, I need a preferred CPU mask on a per IRQ basis. And > yes, that mask may not be restricted to the CPUs of a single NUMA node. > But in the normal case, the mask will be restricted to CPUs of a single > node.
Right, but the normal case does not help much if we need to consider the special case of multiple nodes affected which requires another cpumask in irq_desc. That's what I really want to avoid.
I at least understand the exact problem you guys want to solve. Will think more about it.
Thanks,
tglx
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