Mark A Rada <marada@xxxxxxxxxxxx> writes:
> Ok, so I got a good nights sleep now, and reviewed the results of my
> benchmarks to make sure they were consistent (turns out I had the
> archive sizes in the wrong order for the XZ repository tests).
>
> I also reworded a number of things and added a conclusion to the
> benchmarks.
>
> Let me know what you think.
Well separated change. Very detailed commit message; that's good!.
[...]
> Linux 2.6 series (f5886c7f96f2542382d3a983c5f13e03d7fc5259) 349M
> gzip 23.70s user 0.47s system 99% cpu 24.227 total 76M
> gunzip 3.74s user 0.74s system 94% cpu 4.741 total
> bzip2 130.96s user 0.53s system 99% cpu 2:11.97 total 59M
> bunzip2 31.05s user 1.02s system 99% cpu 32.355 total
> xz 448.78s user 0.91s system 99% cpu 7:31.28 total 51M
> unxz 7.67s user 0.80s system 98% cpu 8.607 total
>
> Git (0a53e9ddeaddad63ad106860237bbf53411d11a7) 11M
> gzip 0.77s user 0.03s system 99% cpu 0.792 total 2.5M
> gunzip 0.12s user 0.02s system 98% cpu 0.142 total
> bzip2 3.42s user 0.02s system 99% cpu 3.454 total 2.1M
> bunzip2 0.95s user 0.03s system 99% cpu 0.984 total
> xz 12.88s user 0.14s system 98% cpu 13.239 total 1.9M
> unxz 0.27s user 0.03s system 99% cpu 0.298 total
>
> XZ (669413bb2db954bbfde3c4542fddbbab53891eb4) 1.8M
> gzip 0.12s user 0.00s system 95% cpu 0.132 total 442K
> gunzip 0.02s user 0.00s system 97% cpu 0.027 total
> bzip2 1.28s user 0.01s system 99% cpu 1.298 total 363K
> bunzip2 0.15s user 0.01s system 100% cpu 0.157 total
> xz 1.62s user 0.03s system 99% cpu 1.652 total 347K
> unxz 0.05s user 0.00s system 99% cpu 0.058 total
Note that for me the above results are not aligned in table.
This is a cosmetic issue.
> Purely from a time and memory perspective, nothing compares to GZip in
> each of the three tests. Though, if you have an average upload speed of
> 20KB/s, it would take ~400 seconds longer to transfer the kernel
> snapshot
> that was BZip2 compressed than it would the XZ compressed snapshot, the
> transfer time difference is even greater when compared to the GZip
> compressed snapshot. The wall clock time savings are relatively the same
> for all test cases, but less dramatic for the smaller repositories.
>
> The obvious downside for XZ compressed snapshots is the large CPU and
> memory load put on the server to actualy generate the snapshot. Though
> XZ
> will eventually have good threading support, and I suspect then that the
> wall clock time for making an XZ compressed snapshot would go down
> considerably if the server had a beefy multi-core CPU.
>
> I have not enabled XZ compression by default because the current default
> is GZip, and XZ is only really competitive with BZip2. Also, the XZ
> format
> is still fairly new (the format was declared stable about 6 months ago),
> and there have been no "stable" releases of the utils yet.
Those above three paragraphs are strangely wrapped, with single word
for a whole line ('snapshot', 'XZ', 'format'). This is a cosmetic issue.
>
> Signed-off-by: Mark Rada <marada@xxxxxxxxxxxx>
--
Jakub Narebski
Git User's Survey 2009: http://tinyurl.com/GitSurvey2009
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