Importance of HTTP connection keep-alive (was: Is this for real?)

Fabian Keil freebsd-listen at fabiankeil.de
Wed Apr 11 19:26:21 UTC 2007


"Michael_google gmail_Gersten" <keybounce at gmail.com> wrote:

> (Yea, getting keep-alive to work will help a lot with web browsing,

Is this an assumption or did you just forget to show
your benchmarks to back this claim up?

> but that means tossing privoxy and using something else.

Actually you can use connection keep-alive without tossing
Privoxy. Just put Polipo between Privoxy and Tor (be aware
that using another proxy behind Privoxy will render some of
Privoxy's actions useless, though).

My impression is that keep-alive (in the setup described
above, and without Privoxy in the chain) doesn't buy you
enough to be noticeable.

Of course adding Polipo to the proxy chain has other
advantages, I didn't do any scientific benchmarks either,
and I may be biased.


I used Privoxy's CVS version to measure the effects of not
having to use prevent-compression for filtering, though:

fk at TP51 ~ $head -n 15000 /usr/jails/privoxy-jail/var/log/privoxy/privoxy.log | grep Decomp | privoxy-log-parser    
16:50:26.413 0815c700 Re-Filter: Decompression successful. Old size: 1147, new size: 2763. (saved: 58.49%)
16:50:27.125 0815c800 Re-Filter: Decompression successful. Old size: 5007, new size: 20885. (saved: 76.03%)
16:50:27.704 0808e900 Re-Filter: Decompression successful. Old size: 623, new size: 2145. (saved: 70.96%)
16:51:48.746 0815c900 Re-Filter: Decompression successful. Old size: 6104, new size: 26928. (saved: 77.33%)
16:57:07.983 0815c900 Re-Filter: Decompression successful. Old size: 29972, new size: 148272. (saved: 79.79%)
16:57:08.745 0815c600 Re-Filter: Decompression successful. Old size: 24125, new size: 113632. (saved: 78.77%)
16:57:16.002 0815ca00 Re-Filter: Decompression successful. Old size: 30392, new size: 150126. (saved: 79.76%)
16:57:17.475 0815c100 Re-Filter: Decompression successful. Old size: 15979, new size: 78088. (saved: 79.54%)
16:57:42.869 08156000 Re-Filter: Decompression successful. Old size: 18927, new size: 86616. (saved: 78.15%)
16:57:50.084 0808e700 Re-Filter: Decompression successful. Old size: 23686, new size: 115163. (saved: 79.43%)
16:58:32.836 0815c400 Re-Filter: Decompression successful. Old size: 30261, new size: 141889. (saved: 78.67%)
17:15:53.644 0808e700 Re-Filter: Decompression successful. Old size: 5318, new size: 22906. (saved: 76.78%)
17:22:20.633 0815c100 Re-Filter: Decompression successful. Old size: 7351, new size: 36324. (saved: 79.76%)

As receiving compressed content seldom saves less than 50%,
I assume that for Privoxy 3.0.6 (chained with Tor) the missing
zlib support is a much bigger slow-down factor than the missing
support for connection keep-alive (if that's a slow-down factor
at all).

Fabian
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