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https://github.com/luxfi/zapdb.git
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Andy KimballandManish R Jain
eeccca45f4
* Allocate nodes from the arena. The skiplist allocates keys and values from the arena, but not nodes. This change begins allocating nodes from the arena. Links between nodes at the same level are now offsets into the arena rather than pointers. The "tower" of links is allocated as extra bytes appended to the end of the node rather than a separate array. Together, these changes significantly speed up skiplist writes and reads. It also reduces overall memory usage (by using next offsets rather than next pointers), as well as GC pressure (nodes do not use pointers to reference one another). * Allocate full tower in node struct. The current code allocates the first tower entry in the node struct and then allocates additional entries beyond the end of the node. This change instead allocates all the tower entries as part of the node struct, and then allocates only a subset of those entries in the arena. This makes the code slightly simpler (no unsafeTower).
This is much better than skiplist and slist.
BenchmarkReadWrite/frac_0-8 3000000 537 ns/op
BenchmarkReadWrite/frac_1-8 3000000 503 ns/op
BenchmarkReadWrite/frac_2-8 3000000 492 ns/op
BenchmarkReadWrite/frac_3-8 3000000 475 ns/op
BenchmarkReadWrite/frac_4-8 3000000 440 ns/op
BenchmarkReadWrite/frac_5-8 5000000 442 ns/op
BenchmarkReadWrite/frac_6-8 5000000 380 ns/op
BenchmarkReadWrite/frac_7-8 5000000 338 ns/op
BenchmarkReadWrite/frac_8-8 5000000 294 ns/op
BenchmarkReadWrite/frac_9-8 10000000 268 ns/op
BenchmarkReadWrite/frac_10-8 100000000 26.3 ns/op
And even better than a simple map with read-write lock:
BenchmarkReadWriteMap/frac_0-8 2000000 774 ns/op
BenchmarkReadWriteMap/frac_1-8 2000000 647 ns/op
BenchmarkReadWriteMap/frac_2-8 3000000 605 ns/op
BenchmarkReadWriteMap/frac_3-8 3000000 603 ns/op
BenchmarkReadWriteMap/frac_4-8 3000000 556 ns/op
BenchmarkReadWriteMap/frac_5-8 3000000 472 ns/op
BenchmarkReadWriteMap/frac_6-8 3000000 476 ns/op
BenchmarkReadWriteMap/frac_7-8 3000000 457 ns/op
BenchmarkReadWriteMap/frac_8-8 5000000 444 ns/op
BenchmarkReadWriteMap/frac_9-8 5000000 361 ns/op
BenchmarkReadWriteMap/frac_10-8 10000000 212 ns/op
Node Pooling
Command used
rm -Rf tmp && /usr/bin/time -l ./populate -keys_mil 10
For pprof results, we run without using /usr/bin/time. There are four runs below.
Results seem to vary quite a bit between runs.
Before node pooling
1311.53MB of 1338.69MB total (97.97%)
Dropped 30 nodes (cum <= 6.69MB)
Showing top 10 nodes out of 37 (cum >= 12.50MB)
flat flat% sum% cum cum%
523.04MB 39.07% 39.07% 523.04MB 39.07% github.com/dgraph-io/badger/skl.(*Skiplist).Put
184.51MB 13.78% 52.85% 184.51MB 13.78% runtime.stringtoslicebyte
166.01MB 12.40% 65.25% 689.04MB 51.47% github.com/dgraph-io/badger/mem.(*Table).Put
165MB 12.33% 77.58% 165MB 12.33% runtime.convT2E
116.92MB 8.73% 86.31% 116.92MB 8.73% bytes.makeSlice
62.50MB 4.67% 90.98% 62.50MB 4.67% main.newValue
34.50MB 2.58% 93.56% 34.50MB 2.58% github.com/dgraph-io/badger/table.(*BlockIterator).parseKV
25.50MB 1.90% 95.46% 100.06MB 7.47% github.com/dgraph-io/badger/y.(*MergeIterator).Next
21.06MB 1.57% 97.04% 21.06MB 1.57% github.com/dgraph-io/badger/table.(*Table).read
12.50MB 0.93% 97.97% 12.50MB 0.93% github.com/dgraph-io/badger/table.header.Encode
128.31 real 329.37 user 17.11 sys
3355660288 maximum resident set size
0 average shared memory size
0 average unshared data size
0 average unshared stack size
2203080 page reclaims
764 page faults
0 swaps
275 block input operations
76 block output operations
0 messages sent
0 messages received
0 signals received
49173 voluntary context switches
599922 involuntary context switches
After node pooling
1963.13MB of 2026.09MB total (96.89%)
Dropped 29 nodes (cum <= 10.13MB)
Showing top 10 nodes out of 41 (cum >= 185.62MB)
flat flat% sum% cum cum%
658.05MB 32.48% 32.48% 658.05MB 32.48% github.com/dgraph-io/badger/skl.glob..func1
297.51MB 14.68% 47.16% 297.51MB 14.68% runtime.convT2E
257.51MB 12.71% 59.87% 257.51MB 12.71% runtime.stringtoslicebyte
249.01MB 12.29% 72.16% 1007.06MB 49.70% github.com/dgraph-io/badger/mem.(*Table).Put
142.43MB 7.03% 79.19% 142.43MB 7.03% bytes.makeSlice
100MB 4.94% 84.13% 758.05MB 37.41% github.com/dgraph-io/badger/skl.newNode
99.50MB 4.91% 89.04% 99.50MB 4.91% main.newValue
75MB 3.70% 92.74% 75MB 3.70% github.com/dgraph-io/badger/table.(*BlockIterator).parseKV
44.62MB 2.20% 94.94% 44.62MB 2.20% github.com/dgraph-io/badger/table.(*Table).read
39.50MB 1.95% 96.89% 185.62MB 9.16% github.com/dgraph-io/badger/y.(*MergeIterator).Next
135.58 real 374.29 user 17.65 sys
3740614656 maximum resident set size
0 average shared memory size
0 average unshared data size
0 average unshared stack size
2276566 page reclaims
770 page faults
0 swaps
128 block input operations
90 block output operations
0 messages sent
0 messages received
0 signals received
46434 voluntary context switches
597049 involuntary context switches