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

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Message-ID: <20250106113123.0000384b@gmail.com>
Date: Mon, 6 Jan 2025 11:31:23 +0800
From: Furong Xu <0x1207@...il.com>
To: Jason Xing <kerneljasonxing@...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, 6 Jan 2025 11:15:45 +0800, Jason Xing <kerneljasonxing@...il.com> wrote:

> 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?

A x86 PC send out UDP packet and the sar cmd from Sysstat package to report
the PPS on RX side:
sar -n DEV 60 1