netdev - Re: [PATCH v2 net-next 4/5] xps_flows: XPS for packets that don't have a socket

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Message-ID: <1475160695.28155.168.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 29 Sep 2016 07:51:35 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Tom Herbert <tom@...bertland.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Rick Jones <rick.jones2@....com>,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCH v2 net-next 4/5] xps_flows: XPS for packets that don't
 have a socket

On Thu, 2016-09-29 at 10:08 -0400, Tom Herbert wrote:

> It addresses  the issue that Rick Jones pointed out was happening with
> XPS. When packets are sent for a flow that has no socket and XPS is
> enabled then each packet uses the XPS queue based on the running CPU.
> Since the thread sending on a flow can be rescheduled on different
> CPUs this is creating ooo packets. In this case the ooo is being
> caused by interaction with XPS.
> 

Nope, your patch does not address the problem properly.

I am not sure I want to spend more time explaining the issue.

Lets talk about this in Tokyo next week.