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SubjectRe: [PATCH 00/13] ibmvfc: initial MQ development
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On 11/26/20 2:48 AM, Tyrel Datwyler wrote:
> Recent updates in pHyp Firmware and VIOS releases provide new infrastructure
> towards enabling Subordinate Command Response Queues (Sub-CRQs) such that each
> Sub-CRQ is a channel backed by an actual hardware queue in the FC stack on the
> partner VIOS. Sub-CRQs are registered with the firmware via hypercalls and then
> negotiated with the VIOS via new Management Datagrams (MADs) for channel setup.
>
> This initial implementation adds the necessary Sub-CRQ framework and implements
> the new MADs for negotiating and assigning a set of Sub-CRQs to associated VIOS
> HW backed channels. The event pool and locking still leverages the legacy single
> queue implementation, and as such lock contention is problematic when increasing
> the number of queues. However, this initial work demonstrates a 1.2x factor
> increase in IOPs when configured with two HW queues despite lock contention.
>
Why do you still hold the hold lock during submission?
An initial check on the submission code path didn't reveal anything
obvious, so it _should_ be possible to drop the host lock there.
Or at least move it into the submission function itself to avoid lock
contention. Hmm?

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

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