netdev - Re: [PATCH net-next RFC] net: ethernet: mtk_eth

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Message-ID: <CA+SN3soUH9dxAkKD8AB64Ay48T=Dj-QFftMoMLZfVGH+Q1mjzA@mail.gmail.com>
Date: Mon, 22 Jul 2024 21:04:06 +0300
From: Elad Yifee <eladwf@...il.com>
To: Joe Damato <jdamato@...tly.com>, Elad Yifee <eladwf@...il.com>, daniel@...rotopia.org, 
	Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>, 
	Mark Lee <Mark-MC.Lee@...iatek.com>, Lorenzo Bianconi <lorenzo@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next RFC] net: ethernet: mtk_eth_soc: use prefetch methods

On Mon, Jul 22, 2024 at 7:17 PM Joe Damato <jdamato@...tly.com> wrote:
>
> On Sat, Jul 20, 2024 at 07:46:18PM +0300, Elad Yifee wrote:
> > Utilize kernel prefetch methods for faster cache line access.
> > This change boosts driver performance,
> > allowing the CPU to handle about 5% more packets/sec.
>
> Nit: It'd be great to see before/after numbers and/or an explanation of
> how you measured this in the commit message.
Sure, I'll add iperf3 results in the next version.

> Is there any reason to mix net_prefetch (as you have below) with
> prefetch and prefetchw ?
>
> IMHO: you should consider using net_prefetch and net_prefetchw
> everywhere instead of using both in your code.
You are right, honestly I didn't notice it exists.
I'll replace all prefetchw with net_prefetchw.

> > @@ -2039,7 +2040,7 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
> >               idx = NEXT_DESP_IDX(ring->calc_idx, ring->dma_size);
> >               rxd = ring->dma + idx * eth->soc->rx.desc_size;
> >               data = ring->data[idx];
> > -
> > +             prefetch(rxd);
>
> Maybe net_prefetch instead, as mentioned above?
This is the only case where I think prefetch should be used since it's
only the descriptor.

Thank you for your suggestions