netdev - Re: [PATCH 1/3, net-next] net: netsec: Use page

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Date:   Fri, 28 Jun 2019 20:19:34 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     David Miller <davem@...emloft.net>
Cc:     brouer@...hat.com, netdev@...r.kernel.org,
        jaswinder.singh@...aro.org, ard.biesheuvel@...aro.org,
        bjorn.topel@...el.com, magnus.karlsson@...el.com,
        daniel@...earbox.net, ast@...nel.org,
        makita.toshiaki@....ntt.co.jp, jakub.kicinski@...ronome.com,
        john.fastabend@...il.com, maciejromanfijalkowski@...il.com
Subject: Re: [PATCH 1/3, net-next] net: netsec: Use page_pool API

Hi David, 

> >> Use page_pool and it's DMA mapping capabilities for Rx buffers instead
> >> of netdev/napi_alloc_frag()
> >> 
> >> Although this will result in a slight performance penalty on small sized
> >> packets (~10%) the use of the API will allow to easily add XDP support.
> >> The penalty won't be visible in network testing i.e ipef/netperf etc, it
> >> only happens during raw packet drops.
> >> Furthermore we intend to add recycling capabilities on the API
> >> in the future. Once the recycling is added the performance penalty will
> >> go away.
> >> The only 'real' penalty is the slightly increased memory usage, since we
> >> now allocate a page per packet instead of the amount of bytes we need +
> >> skb metadata (difference is roughly 2kb per packet).
> >> With a minimum of 4BG of RAM on the only SoC that has this NIC the
> >> extra memory usage is negligible (a bit more on 64K pages)
> >> 
> >> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> >> ---
> >>  drivers/net/ethernet/socionext/Kconfig  |   1 +
> >>  drivers/net/ethernet/socionext/netsec.c | 121 +++++++++++++++---------
> >>  2 files changed, 75 insertions(+), 47 deletions(-)
> > 
> > Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>
> 
> Jesper this is confusing, you just asked if the code needs to be moved
> around to be correct and then right now immediately afterwards you ACK
> the patch.
I can answer on the driver, page_pool_free() needs re-arranging indeed.
I'll fix it and post a V2. I guess Jesper meant 'acked-if-fixed' so i can it on
V2


Thanks
/Ilias