netdev - Re: [PATCH 4/4] bgmac: fix DMA rx corruption

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Message-ID: <552AAB50.7010401@openwrt.org>
Date:	Sun, 12 Apr 2015 19:28:48 +0200
From:	Felix Fietkau <nbd@...nwrt.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev@...r.kernel.org, zajec5@...il.com, hauke@...ke-m.de
Subject: Re: [PATCH 4/4] bgmac: fix DMA rx corruption

On 2015-04-12 19:24, Eric Dumazet wrote:
> On Sun, 2015-04-12 at 12:43 +0200, Felix Fietkau wrote:
>> On 2015-04-12 12:31, Eric Dumazet wrote:
> 
>> > This might be better for performance to perform one single bgmac_write()
>> > at the end of bgmac_dma_rx_read(), and leave this one in place as well,
>> > not for performance since this is slow path, but correctness.
>> I intentionally made it write this field for every slot update, because
>> it might potentially allow the hardware to push frames faster when under
>> pressure. The CPU isn't fast enough to handle gigabit speeds anyway.
> 
> If CPU is not fast enough, then it makes sense to optimize this part,
> and save cpu cycles for actual processing.
> 
> You know, even a fast cpu is not able to keep up at 40Gbits.
> 
> You have a clear opportunity to have batching right there, take it.
Already did that in v2. :)

- Felix
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