netdev - Re: [RFC PATCH] net: Require socket to allow XPS to set queue mapping

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Message-ID: <3fd7a334-c660-6e31-1466-27b08a2c983f@hpe.com>
Date:   Thu, 25 Aug 2016 13:32:12 -0700
From:   Rick Jones <rick.jones2@....com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [RFC PATCH] net: Require socket to allow XPS to set queue mapping

On 08/25/2016 12:49 PM, Eric Dumazet wrote:
> On Thu, 2016-08-25 at 12:23 -0700, Alexander Duyck wrote:
>> A simpler approach is provided with this patch.  With it we disable XPS any
>> time a socket is not present for a given flow.  By doing this we can avoid
>> using XPS for any routing or bridging situations in which XPS is likely
>> more of a hinderance than a help.
>
> Yes, but this will destroy isolation for people properly doing VM cpu
> pining.

Why not simply stop enabling XPS by default. Treat it like RPS and RFS 
(unless I've missed a patch...). The people who are already doing the 
extra steps to pin VMs can enable XPS in that case.  It isn't clear that 
one should always pin VMs - for example if a (public) cloud needed to 
oversubscribe the cores.

happy benchmarking,

rick jones