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From: Trond Myklebust <trond.myklebust@fys.uio.no>
Organization: Dept. of Physics, University of Oslo, Norway
To: kuznet@ms2.inr.ac.ru
Subject: Re: Fragment flooding in 2.4.x/2.5.x
Date: Fri, 28 Jun 2002 12:38:39 +0200
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On Friday 28 June 2002 10:22, Trond Myklebust wrote:

> > Repeating the third time in hope you eventually read the mail to the end:
> > >>>Better way exists. Just use forced sock_wmalloc instead of
> > >>>sock_alloc_send_skb on non-blocking send of all the fragments
> > >>>but the first.
> Attached is a patch that I hope you will comment on (without too many
> expletives please ;-))...

After fixing the missing brackets around (flags&MSG_DONTWAIT), I did some 
tests. I did some NFS writes to a Solaris server, write size = 32k, UDP, over 
a switched 100Mbit/s network. Tests were done using the iozone program (see 
http://www.iozone.org) 'iozone -c -e -t1 -s 120m -r128k'

 - With an ordinary kernel without the patch, I saw average write speeds of 
~2MB/s (peaking at ~2.5MB/s in one trial).

 - With the same kernel, but applying the sock_wmalloc() patch, write speeds 
suddenly jump to ~4.5MB/s (peak was 5MB/s).

... and yes, I did reboot several times in order to switch between the 2 
kernels in order to check repeatability.

I did not expect the effect to be so large, and certainly I can't explain it, 
however I hope you agree that it shows that fixing this bug *is* worth the 
effort.

Cheers,
  Trond
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