Cmt: [SRU][B/aws, F/aws, G/aws][PATCH 0/1] aws: fix network performance regression due to initial TCP buffer size change

[William Breathitt Gray]

On Tue, Jan 05, 2021 at 08:53:51AM +0000, Colin Ian King wrote:
> On 05/01/2021 07:44, Andrea Righi wrote:
> > BugLink: https://bugs.launchpad.net/bugs/1910200
> > 
> > [Impact]
> > 
> > AWS has seen some customers reporting networking performance degradation
> > after they upgraded their Ubuntu instanceses. This regression is highly
> > impacting customers who are using MTU=9000 (which is the default in
> > EC2).
> > 
> > [Test case]
> > 
> > Bug reproduced internally in AWS (no test case provided), but apparently
> > it is very easy to reproduce simply by measuring networking performance.
> > 
> > [Fix]
> > 
> > AWS worked internally and found that this regression has been introduced
> > by:
> > 
> >  a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB")
> > 
> > To solve this problem we need to apply the following upstream commit
> > that explicitly fixes the problem introduced by the commit above:
> > 
> >  33ae7b5bb841 ("tcp: select sane initial rcvq_space.space for big MSS")
> > 
> > [Regression potential]
> > 
> > Upstream fix that is only affecting the initial TCP buffer space and
> > allows the TCP window size to be dynamically increased, basically
> > restoring the previous (correct) behavior, so regression potential is
> > minimal.
> > 
> > 
> I can't seem to find the upstream fix from the sha 33ae7b5bb841, is that
> a typo?  Also, does it make sense to apply this for non-AWS kernels too?
> 
> Colin

Looks like the correct id is sha 72d05c00d7ec.

William Breathitt Gray
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