Re: merge struct ib_device_attr into struct ib_device V2

[Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 10/21/2015 9:38 AM, Christoph Hellwig wrote:
> On Tue, Oct 20, 2015 at 06:07:31PM +0300, Or Gerlitz wrote:
>> >But this makes struct ib_device much much bigger, and this structure
>> >is used in **fast** path,
>> >e.g the ULP traverses through a pointer from struct ib_device to
>> >post_send/recv, poll_cq and friends.
> But it doesn't get near the end of the structure.  Maybe it's time for a
> little cache line 101 primer?

Oh, not that I am fully qualified on that front, but I understand  the 
end-of-structure argument.

Fact is that for struct net_device you will not add 333 new fields over 
night in the coming 33 years, for sure.

This makes much sense to me, as a guideline. I don't think we should 
have a device structure with the current
100 fields and another few hundreds without any notable benefit and 
against the common practice in the networking
subsystem.

We have a UAPI that requires us to keep the device query verb for ever, 
and hence the returned device attr struct,
it would be a much smaller and noisy patch to cache an device attr 
pointer on the device structure.

Or.


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