> On Sep 5, 2017, at 4:06 PM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Sep 05, 2017 at 01:00:10PM -0400, Chuck Lever wrote: > >> - Send completions are batched to reduce interrupts, but still >> provide a periodic heartbeat signal for SQ housekeeping > > I would scrub this commentary, it is very misleading. > > The idea of a periodic completion does not match how verbs works at > all, it was an incomplete root cause analysis from a HCA that uses > different rules for freeing space in the SQ. I think it does bear mentioning that, given this diagnosis, it is still safe to remove the ib_post_send counting mechanism in 5/5, which has been in xprtrdma for as long as I can recall, and has been effective (with a few minor adjustments) at preventing SQ overflow. I'm not able to test this change with every HCA the Linux kernel currently supports, unfortunately. The best I can do is offer a "proof of correctness" and hope that vendors will jump on this and try it out. > Instead, I would say this series creates strong SQ accounting and > properly guarentees the SQ can never overflow by only releasing SQ's > back into the pool when the HCA has confirmed they are completed via a > CQ. I will adjust the cover letter (and patch descriptions as necessary) next time I post this series. Thanks for your suggestions and review. -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
