Re: [RFC PATCH net-next] net: ppp: convert to IFF_NO_QUEUE

[Simon Horman <horms@kernel.org>]

On Tue, Nov 05, 2024 at 12:47:27PM +0100, Toke Høiland-Jørgensen wrote:
> Simon Horman <horms@kernel.org> writes:
> 
> > + Toke
> >
> > On Tue, Oct 29, 2024 at 06:36:56PM +0800, Qingfang Deng wrote:
> >> When testing the parallel TX performance of a single PPPoE interface
> >> over a 2.5GbE link with multiple hardware queues, the throughput could
> >> not exceed 1.9Gbps, even with low CPU usage.
> >> 
> >> This issue arises because the PPP interface is registered with a single
> >> queue and a tx_queue_len of 3. This default behavior dates back to Linux
> >> 2.3.13, which was suitable for slower serial ports. However, in modern
> >> devices with multiple processors and hardware queues, this configuration
> >> can lead to congestion.
> >> 
> >> For PPPoE/PPTP, the lower interface should handle qdisc, so we need to
> >> set IFF_NO_QUEUE. For PPP over a serial port, we don't benefit from a
> >> qdisc with such a short TX queue, so handling TX queueing in the driver
> >> and setting IFF_NO_QUEUE is more effective.
> >> 
> >> With this change, PPPoE interfaces can now fully saturate a 2.5GbE link.
> >> 
> >> Signed-off-by: Qingfang Deng <dqfext@gmail.com>
> >
> > Hi Toke,
> >
> > I'm wondering if you could offer an opinion on this.
> 
> Hi Simon
> 
> Thanks for bringing this to my attention; I'll reply to the parent
> directly :)

Likewise, thanks for following-up on this.