Re: kern/55567: tcp-send slows down to slow single byte transfers (analysis and fix)

[Jason Thorpe <thorpej%me.com@localhost>]

The following reply was made to PR kern/55567; it has been noted by GNATS.

From: Jason Thorpe <thorpej%me.com@localhost>
To: Frank Kardel <kardel%netbsd.org@localhost>
Cc: kern-bug-people%netbsd.org@localhost,
 gnats-admin%netbsd.org@localhost,
 netbsd-bugs%netbsd.org@localhost,
 gnats-bugs%netbsd.org@localhost
Subject: Re: kern/55567: tcp-send slows down to slow single byte transfers
 (analysis and fix)
Date: Wed, 2 Sep 2020 07:58:52 -0700

 > On Sep 2, 2020, at 1:05 AM, Frank Kardel <kardel%netbsd.org@localhost> wrote:
 >=20
 > The path taken that leads to SND.WL2 being starved out is the pure ACK=20=
 
 > section
 > which adjusts the send buffer, updates SND.UNA, SND.FACK, SND.HIGH,=20
 > frees mbuf
 > , send more data if available and returns.
 > SND.WL2 is never touched here an so a longer sequence can leave =
 SND.WL2=20
 > far enough
 > behind for the stuck zero window size to occur.
 >=20
 > Proposed fix:
 
 Frank --
 
 This analysis looks right to me, and your proposed fix looks correct.  =
 It looks like FreeBSD also has an equivalent assignment to SND.WL2 in =
 the same spot for quite a while now, so I would say the change has had =
 some solid bake time already.  Ship it!
 
 -- thorpej