RE: [PATCH V1 net 2/2] net: ena: fix too long default tx interrupt moderation interval

["Kiyanovski, Arthur" <akiyano@amazon.com>]

> -----Original Message-----
> From: David Miller <davem@davemloft.net>
> Sent: Monday, November 4, 2019 9:19 PM
> To: Kiyanovski, Arthur <akiyano@amazon.com>
> Cc: netdev@vger.kernel.org; Woodhouse, David <dwmw@amazon.co.uk>;
> Machulsky, Zorik <zorik@amazon.com>; Matushevsky, Alexander
> <matua@amazon.com>; Bshara, Saeed <saeedb@amazon.com>; Wilson,
> Matt <msw@amazon.com>; Liguori, Anthony <aliguori@amazon.com>;
> Bshara, Nafea <nafea@amazon.com>; Tzalik, Guy <gtzalik@amazon.com>;
> Belgazal, Netanel <netanel@amazon.com>; Saidi, Ali
> <alisaidi@amazon.com>; Herrenschmidt, Benjamin <benh@amazon.com>;
> Dagan, Noam <ndagan@amazon.com>; Agroskin, Shay
> <shayagr@amazon.com>
> Subject: Re: [PATCH V1 net 2/2] net: ena: fix too long default tx interrupt
> moderation interval
> 
> From: <akiyano@amazon.com>
> Date: Mon, 4 Nov 2019 13:58:48 +0200
> 
> > From: Arthur Kiyanovski <akiyano@amazon.com>
> >
> > Current default non-adaptive tx interrupt moderation interval is 196 us.
> > This commit sets it to 0, which is much more sensible as a default value.
> > It can be modified using ethtool -C.
> >
> > Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
> 
> I do not agree that turning TX interrupt moderation off completely is a more
> sensible default value.
> 
> Maybe a much smaller value, but turning off the coalescing delay completely
> is a bit much.

David,
Up until now, the ENA device did not support interrupt moderation, so effectively the default tx interrupt moderation interval was 0.
You are probably right that 0 is not an optimal value.
However until we research and find such an optimal value, in order to avoid a degradation in default performance, we want the default value in the new driver to be (effectively) the same as in the old driver.