Involve more log compression techniques.

Involve more log compression techniques.

Code addresses are now written as an offset from the previous address for ticks, code move and delete events. Employed backreference and RLE compression for code move and delete events. This gives additional 30% log size reduction for benchmarks run w/o snapshot.

Overall compression results (compared with the revision of V8 having no compression):
 - V8: 70% size reduction for benchmarks run w/o snapshot (for reference, gzip gives 87%)
 - Chromium: 65% size reduction for public html version of benchmarks (v4) (for reference, gzip gives 90%)

The one obvious opportunity for improving compression results in Chromium is to compress URLs of scripts.

Committed: http://code.google.com/p/v8/source/detail?r=2162

[Søren Thygesen Gjesse, 2009-06-15 09:32:02]

LGTM

I don't see a test of the encoding of the code addresses for ticks, code move
and delete events using offsets.

[Mikhail Naganov, 2009-06-15 09:37:19]

On 2009/06/15 09:32:02, Søren Gjesse wrote:
> LGTM
> 
> I don't see a test of the encoding of the code addresses for ticks, code move
> and delete events using offsets.

Thanks!

Yes, those tests are absent. But I'm not considering writing them in this CL,
because offsets compression is quite trivial.