Re: Kernel SCM saga..

Ingo Molnar
2005-04-10T12:04:05Z

* Paul Jackson <pj@engr.sgi.com> wrote:

> These 16817 files consume:
>
> 224 MBytes uncompressed and
> 95 MBytes compressed
>
> (using zlib's minigzip, on a 4 KB page reiserfs.)

that's a 42.4% compressed size. Using a (much) more CPU-intense
compression method (bzip -9), the compressed size is down to 45 MBytes.
(a ratio of 20.2%)

using default 'gzip' i get 57 MB compressed.

> Since each change will get its own copy of the file, multiplying these
> two sizes (224 and 95) by 12.2 changes per file means the disk cost
> would be:
>
> 2.73 GByte uncompressed, or
> 1.16 GBytes compressed.

with bzip2 -9 it would be 551 MBytes. It might as well be practical on
faster CPUs, a full tree (224 MBytes, 45 MBytes compressed) decompresses
in 24 seconds on a 3.4GHz P4 - single CPU. (and with dual core likely
becoming the standard, we might as well divide that by two) With default
gzip it's 3.3 seconds though, and that still compresses it down to 57
MB.

Ingo