Hi,
It's been about a month and a half since I started working on S4 and I
guess most of you haven't heard much (unless you've been following the
git commit log) so here's a quick status report.
Backend: The S4-code is mostly done and working. I guess it could need
some cleanup and commenting (especially the B+ tree code) but I most of
the code is in place.
Integration: Inserting S4 instead of SQlite actually went quite
smoothly. Mostly it was a matter of removing medialib_begin/end calls.
The collections were also stored in the medialib, but I rewrote that so
they are saved to {config_dir}/collections/... instead.
(Btw: when I was rewriting collserial.c I saw that the old code made
the assumption that different names in the hashtable could point to the
same collection. I couldn't see a way that would happen so I kinda
skipped it and just handled _active differently. If anyone could
enlighten me and tell me if I was right/wrong that would be great).
Benchmarks: So.. was it all worth it? Well, you tell me:
(Warning: highly unscientific benchmarks)
+---------+------------+------------+-------------+
| Backend | Disk space | List time* | Query time**|
+---------+------------+------------+-------------+
| SQlite | 36.85 MB | ~10.6 s | ~0.22 s |
| S4 | 18.52 MB | ~ 2.0 s | ~0.14 s |
+---------+------------+------------+-------------+
* xmms2 list > /dev/null
** xmms2 mlib search "~foo" AND "id<4000" > /dev/null
The timings were done like this:
time xmms2 {command}
I then calculated server time as real - user, far from perfect I know,
but it gives a general idea.
As you can see just listing all entries in the playlist S4 is about
5 times as fast, or so it would seem, however running it in callgrind
reveals that only about 15% of the time is spent in S4, the rest is
spent packing the values into dicts and whatnot. For SQlite the time
spent inside the backend is ~55%.
The query timing doesn't really tell much, and if someone has some crazy
queries that takes a long time you would probably be able to give some
better benchmarks here.
Drawbacks: You didn't think the performance improvements came for free
did you? The biggest drawback is that S4 isn't ACID-compliant, meaning
we don't guarantee anything. So if your little kid thinks your
powerplug looks like a fun toy and unplugs it all bets are off and you
may lose all data that has not been synced yet. However in most cases
this will not be a big deal as the medialib are mostly just read.
Do you have feedback, ideas, questions or anything else just reply or
drop me a line on IRC.
Cheers,
--
Sivert Berg / cippo
--
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