diff --git a/README.md b/README.md index c153a86..bcb5423 100644 --- a/README.md +++ b/README.md @@ -1,8 +1,8 @@ # bench-lru -benchmark the least-recently-used caches which are available on npm +benchmark the least-recently-used caches which are available on npm. -## introduction +## Introduction An LRU cache is a cache with bounded memory use. The point of a cache is to improve performance, @@ -16,52 +16,42 @@ There is a [previous benchmark](https://www.npmjs.com/package/bench-cache) but it did not describe it's methodology. (and since it measures the memory used, but tests everything in the same process, it does not get clear results) -## method +## Benchmark -I run a very simple benchmark. In three phases, -set the LRU to fit max N=100,000 items, -add N random numbers to the cache, with keys 0-N, -then update those keys with new random numbers, -then _evict_ those keys, by adding keys N-2N. +I run a very simple benchmark. In four phases: -### results +1. set the LRU to fit max N=100,000 items. +2. add N random numbers to the cache, with keys 0-N. +3. then update those keys with new random numbers. +4. then _evict_ those keys, by adding keys N-2N. -Operations per millisecond (higher is better) +### Results -(see updated results at the bottom!) +Operations per millisecond (*higher is better*): -``` csv -name, set, update, evict -lru-native, 621, 901, 654 -modern-lru, 415, 508, 336 -lru-cache, 199, 521, 238 -lru_cache, 2778, 8333, 23 -tiny-lru, 2222, 4000, 23 -lru, 1220, 2128, 7 -simple-lru-cache, 2128, 6250, 7 -mkc, 336, 7, 2 -lru-fast, 6250, 2941, 7 -faster-lru-cache, 1, 1, 1 -secondary-cache, 917, 7, 2 -``` +| name | set | get1 | update | get2 | evict | +| ----------------- | ------- | -------- | --------- | -------- |-------- | +| hashlru | 6250 | 8333 | 6250 | 7143 | 4167 | +| lru-native | 714 | 1053 | 935 | 1042 | 510 | +| modern-lru | 239 | 581 | 498 | 578 | 370 | +| lru-cache | 300 | 1449 | 592 | 1786 | 247 | +| lru_cache | 3226 | 14286 | 11111 | 12500 | 22 | +| lru | 1887 | 2778 | 1724 | 2857 | 7 | +| simple-lru-cache | 3448 | 6667 | 6667 | 9091 | 7 | +| mkc | 410 | 7 | 3 | 2 | 1 | +| lru-fast | 1493 | 4762 | 12500 | 14286 | 7 | +| faster-lru-cache | 1 | 1 | 1 | 1 | 1 | +| secondary-cache | 935 | 7 | 3 | 2 | 1 | -We can group the results in a few categories, + +We can group the results in a few categories: * all rounders (lru-native, modern-lru, lru-cache) where the performance to add update and evict are comparable. * fast-write, slow-evict (lru_cache, tiny-lur, lru, simple-lru-cache, lru-fast) these have better set/update times, but for some reason are quite slow to evict items! * slow in at least 2 categories (mkc, faster-lur-cache, secondary-cache) -## future work - -This is very early results, take any difference smaller than an order of magnitude with a grain of salt. -It is necessary to measure the statistical significance of the results to know accurately the relative -performance of two closely matched implementations. - -I also didn't test the memory usage. This should be done running the benchmarks each in a separate -process, so that the memory used by each run is not left over while the next is running. - -## discussion +## Discussion It appears that all-round performance is the most difficult to achive, and there are no implementations that have very high eviction performance. It is also interesting that of the implementations which @@ -74,31 +64,15 @@ I think there opportunities for better perf. For example, it should be possible when evicting by recycling the least recently used item ito the new value. I would expect this to also have better GC behaviour. -## UPDATE! - -I implemented a new LRU algorithm [hashlru](https://github.com/dominictarr/hashlru) -that is simpler and faster across the board. It's O(1) like LRU, but does less per operation. +## Future work -These results also include read times. +This is very early results, take any difference smaller than an order of magnitude with a grain of salt. -``` csv -name, set, get1, update, get2, evict -hashlru, 6250, 8333, 6250, 7143, 4167 -lru-native, 714, 1053, 935, 1042, 510 -modern-lru, 239, 581, 498, 578, 370 -lru-cache, 300, 1449, 592, 1786, 247 -lru_cache, 3226, 14286, 11111, 12500, 22 -lru, 1887, 2778, 1724, 2857, 7 -simple-lru-cache, 3448, 6667, 6667, 9091, 7 -mkc, 410, 7, 3, 2, 1 -lru-fast, 1493, 4762, 12500, 14286, 7 -faster-lru-cache, 1, 1, 1, 1, 1 -secondary-cache, 935, 7, 3, 2, 1 -``` +It is necessary to measure the statistical significance of the results to know accurately the relative performance of two closely matched implementations. -I removed `tiny-lru` because it was crashing in the get phase. +I also didn't test the memory usage. This should be done running the benchmarks each in a separate process, so that the memory used by each run is not left over while the next is running. -## further discussion +## Further discussion javascript is generally slow, so one of the best ways to make it fast is to write less of it. LRUs are also quite difficult to implement (linked lists!). In trying to come up with a faster @@ -107,9 +81,13 @@ given the strengths and weaknesses of javascript, this is significantly faster t other implementations, _including_ the C implementation. Likely, the overhead of the C<->js boundry is partly to blame here. -## License +## Changelog -MIT +* I implemented a new LRU algorithm [hashlru](https://github.com/dominictarr/hashlru) +that is simpler and faster across the board. It's O(1) like LRU, but does less per operation. +* I removed `tiny-lru` because it was crashing in the get phase. +## License +MIT