Messages in this thread | | | Subject | Re: [PATCH V2] nvme-pci: assign separate irq vectors for adminq and ioq0 | From | "jianchao.wang" <> | Date | Fri, 2 Mar 2018 11:11:22 +0800 |
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Hi Keith
Thanks for your kindly directive and precious time for this.
On 03/01/2018 11:15 PM, Keith Busch wrote: > On Thu, Mar 01, 2018 at 06:05:53PM +0800, jianchao.wang wrote: >> When the adminq is free, ioq0 irq completion path has to invoke nvme_irq twice, one for itself, >> one for adminq completion irq action. > > Let's be a little more careful on the terminology when referring to spec > defined features: there is no such thing as "ioq0". The IO queues start > at 1. The admin queue is the '0' index queue.
Yes, indeed, sorry for my bad description.
>> We are trying to save every cpu cycle across the nvme host path, why we waste nvme_irq cycles here. >> If we have enough vectors, we could allocate another irq vector for adminq to avoid this. > > Please understand the _overwhelming_ majority of time spent for IRQ > handling is the context switches. There's a reason you're not able to > measure a perf difference between IOQ1 and IOQ2: the number of CPU cycles > to chain a second action is negligible. >
Yes, indeed
Sincerely Jianchao
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