[openib-general] CQ peek

[Sean Hefty]

>First, a general point about peek CQ.  For all RDMA device
>architectures that I know of, doing "peek CQ" is just as expensive as
>doing "poll CQ," since the driver needs to do the same locking and
>incur the same cache misses either way.  And then the app will always
>have to do "poll CQ" later anyway.
{snip}
>This is moderately compelling, and if someone has a concrete use for
>poll CQ I'll probably end up implementing it someday (unless someone
>beats me to it).  But I'd be somewhat surprised if a ULP uses a
>primitive that is not defined in either the IB or iWARP verbs.

I vaguely remember discussing peek CQ before, but I don't remember what the
outcome was.  I tend to agree with Roland though.  There are likely mechanisms
to perform the same tasks that can provide better performance.  I would lean
more towards removing peek CQ from the API than implementing it, especially if
it leads an application to be less efficient.

- Sean