netdev - Re: [PATCH] net: core: page_pool: add user refcnt and reintroduce page_pool

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Message-ID: <20190702211536.GA22618@apalos>
Date:   Wed, 3 Jul 2019 00:15:36 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        netdev@...r.kernel.org, grygorii.strashko@...com,
        jakub.kicinski@...ronome.com, daniel@...earbox.net,
        john.fastabend@...il.com, ast@...nel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH] net: core: page_pool: add user refcnt and reintroduce
 page_pool_destroy

Hi Jesper,
Getting late here, i'll respond in detail tomorrow. One point though

[...]
> 
> This special use-case, seems confined to your driver. And Ilias told me
> that XDP is not really a performance benefit for this driver as the HW
> PPS-limit is hit before the XDP and netstack limit.  I ask, does it
> make sense to add XDP to this driver, if it complicates the code for
> everybody else?
I think yes. This is a widely used driver on TI embedded devices so having XDP 
to play along is a nice feature. It's also the first and only armv7 we have
supporting this. Ivan already found a couple of issues due to the 32-bit
architecture he is trying to fix, i think there's real benefit in having that,
performance aside.
I fully agree we should not impact the performance of the API to support a
special hardware though. I'll have a look on the 2 solutions tomorrow, but the
general approach on this one should be 'the simpler the better'

Cheers
/Ilias

> 
> -- 
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer