netdev - Re: mlx5 broken affinity

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Message-ID: <56ae54cd-3ca5-4b31-4c9d-035fbf9d0474@grimberg.me>
Date:   Thu, 9 Nov 2017 17:40:43 +0200
From:   Sagi Grimberg <sagi@...mberg.me>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jes Sorensen <jsorensen@...com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@....mellanox.co.il>,
        Networking <netdev@...r.kernel.org>,
        Leon Romanovsky <leonro@...lanox.com>,
        Kernel Team <kernel-team@...com>,
        Christoph Hellwig <hch@....de>
Subject: Re: mlx5 broken affinity


>> Again, I think Jes or others can provide more information.
> 
> Sagi, I believe Jes is not trying to argue about what initial affinity
> values you give to the driver, We have a very critical regression that
> is afflicting Live systems today and common tools that already exists
> in various distros, such as irqblanace which solely depends on
> smp_affinity sysfs entry which is now not write-able due to this
> regression. please see https://github.com/Irqbalance/irqbalance/blob/ma
> ster/activate.c
> 
> Some users would like to have thier network traffic handled in some
> cores and free up other cores for other purposes, you just can't take
> that away from them.
> 
> If revereting mlx5 patches would solve the issue, I am afraid that is
> the solution i am going to go with, until the regression is fixed.

Well, I completely agree with you Saeed, If this is causing regression
for mlx5 users and we can't find a way for managed interface to expose
this knob to userspace, I don't see any other choice as well.