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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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