[wplug] compression

[Bryon Gill]

The Quicktime file was already heavily compressed, so it spent a lot of effort 
for negative gain.  Try again with a more compressible file (an enormous text 
file for instance) and see if you don't get better results.

On Thu, 14 Apr 2005, Michael Semcheski wrote:

> Patrick Wagstrom wrote:
>> The -C flag will tell SSH/SCP to compress stuff.  In general I use it
>>  all the time.  CPUs are so much faster than networks still so
>> compression is your friend.
>
> While I agree that compression is good on a slow network, this is not
> true for fast networks.  As a test, I took a 200Mb
> quicktime file and sent it across my home 100Mb/fd network via scp with
> and without compression.  I later tried gziping this file (same
> compression that ssh uses) and it compressed about 4%.
>
> Without compression, it took 23 seconds (8MB/sec).
> With compression, it took roughly 1 minute and 20 seconds (2.1MB/sec).
>
> So lzw compression does not do a lot for movie files.  Everybody knew
> that.  My next test I took about 250Mb of tar'd php applications (so
> there were some image files, but it was mostly text).  Gzip was able to
> compress it about 60%, (though I didn't use the gzipped file in my tests).
>
> Without compression, it took 28 seconds (8MB/sec).
> With compression, it took about 50 seconds (4.7MB/sec).
>
> So compression over the 100Mb network slowed things considerably.
>
> The thing that surprised me was that I noticed that with compression, my
> CPU usage (Centrino) went up to 50% for most of the transfer.  Without
> compression, it was around 80% for most of the transfer.
>
> This is not the fastest processor on the market, but its well over 1Ghz.
> Even still, it could not keep up with the network.
>
> Mike
>
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