netdev - Re: [net-next, RFC, 4/8] net: core: add recycle capabilities on skbs via page

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Message-ID: <20181208170729.GB25144@lunn.ch>
Date:   Sat, 8 Dec 2018 18:07:29 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Florian Westphal <fw@...len.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Toke Høiland-Jørgensen <toke@...e.dk>,
        ard.biesheuvel@...aro.org, Jason Wang <jasowang@...hat.com>,
        BjörnTöpel <bjorn.topel@...el.com>,
        w@....eu, Saeed Mahameed <saeedm@...lanox.com>,
        mykyta.iziumtsev@...il.com,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [net-next, RFC, 4/8] net: core: add recycle capabilities on skbs
 via page_pool API

> I got other concerns on the patchset though. Like how much memory is
> it 'ok' to keep mapped keeping in mind we are using the streaming
> DMA API. Are we going to affect anyone else negatively by doing so ?

For mvneta, you can expect the target to have between 512Mbyte to
3G. You can take a look at the DT files to get a better feel for this.
All of it should be low enough that it is DMA'able.

These SoCs are often used for WiFi access points, and NAS boxes.  So i
guess the big memory usage on these boxes is the block cache for a NAS
device. So if you want to see the impact of the driver using more
memory, see if disk performance is affected.

	Andrew