Re: [PATCH] Expire sendonly joins (was Re: [PATCH rdma-rc 0/2] Add mechanism for ipoib neigh state change notifications)

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On 09/28/2015 01:10 PM, Jason Gunthorpe wrote:
> On Mon, Sep 28, 2015 at 11:36:11AM -0400, Doug Ledford wrote:
> 
>>> Also broadcast could cause a unecessary reception event on the NICs of
>>> machines that have no interest in this traffic.
>>
>> This is true.  However, I'm trying to balance between several competing
>> issues.  You also stated the revamped multicast code was adding latency
>> and dropped packets into the problem space.  Sending over the broadcast
>> would help with latency.  However, I have an alternative idea for that...
> 
> I think your original idea of broadcast immediately and deferred
> optimal mlid lookup is the best *functionally* for every case - only
> when you enter the very edge world of caring about timing does it make
> any difference.
> 
> Christoph's needs would probably be better served by giving some API
> to control the mlid cache (ie the neightbour table is already 99% of
> the way there). This would let some userspace component pre-load and
> fix all relevant data and undesired cache activity simply can't add
> jitter.

So, I've taken Christoph's patch, added two of my own (just changed the
comment and the #if statement so that we create groups on send-only
joins, and upped the max send-only backlog queue).  We'll leave it at
that for 4.3 and try to address it more fully in 4.4.


-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD



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