netdev - Re: [PATCH net-next v3] page_pool: check for dma_sync

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Message-ID: <CAL+tcoBfZRNrHarZzmRh0ep+QrfZOntm82hECNb=aMO-FdmH8g@mail.gmail.com>
Date: Mon, 6 Jan 2025 11:15:45 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Furong Xu <0x1207@...il.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net-next v3] page_pool: check for dma_sync_size earlier

On Mon, Jan 6, 2025 at 11:02 AM Furong Xu <0x1207@...il.com> wrote:
>
> Setting dma_sync_size to 0 is not illegal, fec_main.c and ravb_main.c
> already did.
> We can save a couple of function calls if check for dma_sync_size earlier.
>
> This is a micro optimization, about 0.6% PPS performance improvement
> has been observed on a single Cortex-A53 CPU core with 64 bytes UDP RX
> traffic test.
>
> Before this patch:
> The average of packets per second is 234026 in one minute.
>
> After this patch:
> The average of packets per second is 235537 in one minute.

Sorry, I keep skeptical that this small improvement can be statically
observed? What exact tool or benchmark are you using, I wonder?

Thanks,
Jason