netdev - Re: [PATCH net] net: stmmac: Use hrtimer for TX coalescing

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Date:   Tue, 24 Nov 2020 08:50:13 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        kernel <kernel@...s.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net: stmmac: Use hrtimer for TX coalescing

On Tue, 24 Nov 2020 05:11:27 +0100 Vincent Whitchurch wrote:
> On Tue, Nov 24, 2020 at 01:46:00AM +0100, Jakub Kicinski wrote:
> > On Fri, 20 Nov 2020 16:02:08 +0100 Vincent Whitchurch wrote:  
> > > This driver uses a normal timer for TX coalescing, which means that the
> > > with the default tx-usecs of 1000 microseconds the cleanups actually
> > > happen 10 ms or more later with HZ=100.  This leads to very low
> > > througput with TCP when bridged to a slow link such as a 4G modem.  Fix
> > > this by using an hrtimer instead.
> > > 
> > > On my ARM platform with HZ=100 and the default TX coalescing settings
> > > (tx-frames 25 tx-usecs 1000), with "tc qdisc add dev eth0 root netem
> > > delay 60ms 40ms rate 50Mbit" run on the server, netperf's TCP_STREAM
> > > improves from ~5.5 Mbps to ~100 Mbps.
> > > 
> > > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>  
> > 
> > Looks perfectly reasonable, but you marked it for net. Do you consider
> > this to be a bug fix, and need it backported to stable? Otherwise I'd
> > rather apply it to net-next.  
> 
> No, sorry, I think a backport to stable is unnecessary.  It should be
> fine to apply it to net-next.  Thanks.

Applied to net-next, thank you!