> -----Original Message----- > From: Yuchung Cheng <[email protected]> > Sent: Tuesday, October 10, 2023 6:27 PM > To: Stephen Hemminger <[email protected]> > Cc: Haiyang Zhang <[email protected]>; [email protected]; > [email protected]; KY Srinivasan <[email protected]>; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; linux- > [email protected]; [email protected]; [email protected] > Subject: Re: [PATCH net-next,v2] tcp: Set pingpong threshold via sysctl > > On Tue, Oct 10, 2023 at 3:14 PM Stephen Hemminger > <[email protected]> wrote: > > > > On Tue, 10 Oct 2023 12:23:30 -0700 > > Haiyang Zhang <[email protected]> wrote: > > > > > TCP pingpong threshold is 1 by default. But some applications, like SQL DB > > > may prefer a higher pingpong threshold to activate delayed acks in quick > > > ack mode for better performance. > > > > > > The pingpong threshold and related code were changed to 3 in the year > > > 2019 in: > > > commit 4a41f453bedf ("tcp: change pingpong threshold to 3") > > > And reverted to 1 in the year 2022 in: > > > commit 4d8f24eeedc5 ("Revert "tcp: change pingpong threshold to 3"") > > > > > > There is no single value that fits all applications. > > > Add net.ipv4.tcp_pingpong_thresh sysctl tunable, so it can be tuned for > > > optimal performance based on the application needs. > > > > > > Signed-off-by: Haiyang Zhang <[email protected]> > > > > If this an application specific optimization, it should be in a socket > > option > > rather than system wide via sysctl. > Initially I had a similar comment but later decided a sysctl could > still be useful if > 1) the entire host (e.g. virtual machine) is dedicated to that application > 2) that application is difficult to change
Yes, the customer actually wants a global setting. But as suggested by Neal, I changed it to be per-namespace to match other TCP tunables. Thanks, - Haiyang
