tdb2: limit coalescing based on how successful we are.
Instead of walking the entire free list, walk 8 entries, or more if we
are successful: the reward is scaled by the size coalesced.
We also move previously-examined records to the end of the list.
This reduces file size with very little speed penalty.
Before:
$ time ./growtdb-bench 250000 10 > /dev/null && ls -l /tmp/growtdb.tdb && time ./tdbtorture -s 0 && ls -l torture.tdb && ./speed --transaction
2000000
real 1m17.022s
user 0m27.206s
sys 0m3.920s
-rw------- 1 rusty rusty
570130576 2011-04-27 21:17 /tmp/growtdb.tdb
testing with 3 processes, 5000 loops, seed=0
OK
real 1m27.355s
user 0m0.296s
sys 0m0.516s
-rw------- 1 rusty rusty 617352 2011-04-27 21:18 torture.tdb
Adding
2000000 records: 890 ns (
110556088 bytes)
Finding
2000000 records: 565 ns (
110556088 bytes)
Missing
2000000 records: 390 ns (
110556088 bytes)
Traversing
2000000 records: 410 ns (
110556088 bytes)
Deleting
2000000 records: 8623 ns (
244003768 bytes)
Re-adding
2000000 records: 7089 ns (
244003768 bytes)
Appending
2000000 records: 33708 ns (
244003768 bytes)
Churning
2000000 records: 2029 ns (
268404160 bytes)
After:
$ time ./growtdb-bench 250000 10 > /dev/null && ls -l /tmp/growtdb.tdb && time ./tdbtorture -s 0 && ls -l torture.tdb && ./speed --transaction
2000000
real 1m7.096s
user 0m15.637s
sys 0m3.812s
-rw------- 1 rusty rusty
561270928 2011-04-27 21:22 /tmp/growtdb.tdb
testing with 3 processes, 5000 loops, seed=0
OK
real 1m13.850s
user 0m0.268s
sys 0m0.492s
-rw------- 1 rusty rusty 429768 2011-04-27 21:23 torture.tdb
Adding
2000000 records: 892 ns (
110556088 bytes)
Finding
2000000 records: 570 ns (
110556088 bytes)
Missing
2000000 records: 390 ns (
110556088 bytes)
Traversing
2000000 records: 407 ns (
110556088 bytes)
Deleting
2000000 records: 706 ns (
244003768 bytes)
Re-adding
2000000 records: 822 ns (
244003768 bytes)
Appending
2000000 records: 1262 ns (
268404160 bytes)
Churning
2000000 records: 2320 ns (
268404160 bytes)