netdev - Re: [RFC net-next 1/2] net: net-porcfs: Reduce rcu lock critical section

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Message-ID: <1523560344.3587.40.camel@mellanox.com>
Date:   Thu, 12 Apr 2018 19:12:27 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "eric.dumazet@...il.com" <eric.dumazet@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC net-next 1/2] net: net-porcfs: Reduce rcu lock critical
 section

On Wed, 2018-04-11 at 19:59 -0700, Eric Dumazet wrote:
> 
> On 04/11/2018 04:47 PM, Saeed Mahameed wrote:
> > 
> > Well if we allow devices to access HW counters via FW command
> > interfaces in ndo_get_stats and by testing mlx5 where we query up
> > to 5
> > hw registers, it could take 100us, still this is way smaller than
> > 10sec
> >  :) and it is really a nice rate to fetch HW stats on demand.
> 
> If hardware stats are slower than software ones, maybe it is time to
> use software stats,
> instead of changing the whole stack ?
> 

We already have SW stats for [rx/tx]_[packets/bytes] but for
[rx/tx]_[error/drop] etc .. they can only be grabbed from HW.

We don't want to report only partial counters to get_stats ndo just to
avoid sleeping.

> There are very few devices drivers having issues like that.
>