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Message-ID: <1400859695.5367.203.camel@edumazet-glaptop2.roam.corp.google.com>
Subject: RE: skbuff truesize incorrect.
From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>
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On Fri, 2014-05-23 at 15:30 +0000, David Laight wrote:
> From: Eric Dumazet
> ...
> > TCP stack uses fast clones, and current stack gives them a truesize of
> > 2048 + sizeof(sk_buff), while it really should be 2048 +
> > 2*sizeof(sk_buff)
> > 
> > Luckily, GSO/TSO tends to reduce the error, as skbs overhead is lower.
> 
> Doesn't that affect the tx side - where the truesize doesn't matter as much?

Its not a matter of tx or rx, but percentage of error.

If truesize accounting is wrong by 10%, its not a big deal, because we
normally limit tcp_mem[] to about 16% of available physical memory.

Using 16% of physical memory instead of 16% should not really matter.

Now, if the truesize is wrong by 1600%, then its pretty clear we can
consume all the meory.