Re: [PATCH RFC 0/5] xprtrdma Send completion batching

Sagi Grimberg
2017-09-06T11:54:20Z

> Hi Jason, Sagi-

Hey Chuck,

> As we discussed a few weeks ago, this patch series implements the
> following:
>
> - Send SGEs are now managed via lock-less, wait-free circular queues
> - Send SGEs referring to page cache pages are DMA unmapped during
> Send completion
> - Send completions are batched to reduce interrupts, but still
> provide a periodic heartbeat signal for SQ housekeeping
> - The circular queue prevents Send Queue overflow
>
> The purpose of this change is to address the issue Sagi reported
> where the HCA continues to retry a delayed Send request _after_ RPC
> completion, resulting in a DMA error.

Question, what happens in direct-io for example? Can a mapped buffer be
reclaimed/free'd before the send completion arrives?
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