isaacs / bench-lru

bench-lru

benchmark the least-recently-used caches which are available on npm.

Update: January, 2022

This is a fork of Dominc Tarr's original bench-lru script. I've made the following modifications.

First, I noted that cache performance and correctness in JavaScript is highly dependent on the types of keys used to store items in the cache.

Specifically:

1. When using keys that aren't strings or symbols, it's possible for keys to collide if using an Object as the backing store rather than a Map.
2. When using integer numbers as object keys, V8 is extremely optimized for Object data storage, especially if the values are also integers. However, if the values are numeric strings but numeric float strings, performance goes out the window.
3. Long strings are much slower Object keys than long strings.

In the real world, it's quite rare to store 200k integers using the exact same 200k integers as keys. This iteration of the benchmark uses a variety of integers, floats, numeric integer strings, numeric float strings, long strings, strings and integers that collide, objects, and so on, and disqualifies caches that don't pass a basic correctness smoke test.

Next, the weighting of scores doesn't much match real world use cases either. In observing several production use cases of LRU caches, the some consistent patterns can be observed.

Typically, an LRUCache is being used (if it is actually needed) for a case where:

1. The total data corpus is very large, and cannot comfortably fit in memory. (If it isn't large, just save it all, don't bother with an LRU.)
2. The time required to fetch any given item is significant. (If it isn't, just fetch it each time, don't bother with an LRU.)
3. The time over which the data will be accessed is significant, and thus the subset of the corpus of data which will eventually need to be accessed is by the process is more than can comfortably fit in memory.
4. Items tend to spike in popularity for a while, then become less frequenty accessed.

If these criteria are met, an LRUCache is a good fit. If a few of them are likely, and the others might be true, then it might still be a good fit to be safe. It's a fairly common need, if somewhat specific.

Given this behavior pattern, the weights in the benchmark were off. Simply reporting updates per ms next to evictions per ms is a bit unhelpful. Dominic was correct that evictions are important.

However, an eviction can only happen at the time of making a set() call, which means that you just performed some expensive upstream action to get the thing that you're caching from its origin.

updates (that is, setting a key which is already in the cache) are extremely rare in normal LRU-friendly workloads. If you already have it in the cache, don't fetch it upstream or write it again, use the cached one. That's the whole point!

The most frequent operations an LRUCache is normally called upon for is: "fetching an item from the queue again".

That is to say, to the greatest extent possible, get() performance should be roughly equivalent, regardless of where in the heirarchy of recency a given item is found. If fetching the most recently used item is fast, but fetching the item 50% most recently used, or even least recently used, is slow, then the cache will perform poorly (and unpredictably!) under real workloads.

To account for the priorities (and the fact that eviction is much slower in every cache measured), the following weights are applied to form a final "score", which is used to sort the list:

1. evict * 5
2. get2 * 5
3. get1 * 3
4. set * 2
5. update * 1

Note that since get2 tends to be much faster than evict in all caches tested, this ends up being the most important metric.

Also, I observed that some caches perform very well when get() calls are made in the order in which they were inserted into the cache, but much more poorly when get() calls are made out of order. Under real workloads, a cache is rarely called upon to list its contents in insertion order, but instead is used in an unpredictable order.

To accomplish this, the ordering of the data used in the update and get2 benchmarks is randomized, so that the items need to be constantly reshuffled, as they would be in a real use case.

Conclusions from this new approach, and my attempts to make lru-cache perform well

1. Only caches with Map-based key stores are capable of handling keys that are long string, numeric float strings, or Symbol objects with adequate performance.

   This was surprising to me! I expected that Symbol objects would perform well in an Object key store, and I suspect that future versions of V8 may optimize this code path if more people use it. The performance gains on long strings (and especially numeric float strings) in Map key stores was somewhat surprising as well, but this just shows the hazard of optimizing for a benchmark instead of making a benchmark match real workloads.

2. Only caches with Map-based key stores are capable of handling non-string/symbol keys correctly.

3. The garbage-collection penalty for throwing away an object (the approach advocated below) is very low for an object full of integer keys and numeric values. However, it rises dramatically for almost any other shape of data, making linked-list style approaches more effective.

4. Similarly, the gc penalty for object-based linked list approaches makes them perform significantly worse than pointer-based linked list approaches.

   That is, it's much faster to implement the linked list as two arrays of integers and do this.next[index] and this.previous[index] rather than an array of node objects and node.next and node.previous. No amount of object optimization (reusing objects from a pool, etc.) seemed able to get around this.

   This wasn't surprising, but it was disappointing. node.next.value is much more ergonomic and readable than this.valueList[this.next[index]].

Almost any of these cache implementations will perform well enough in any situation where you find yourself with a problem that needs a cache. But as always, if you are optimizing a hot path and performance matters, make sure to test it against your actual scenario. If you are strictly using integers as keys, it's worth using one of the "worse" caches on this list.

Results

int: just an integer
| name                                                           | set   | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|-------|-------|--------|-------|-------|--------|
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 27663 | 63492 | 8780   | 59880 | 6425  | 586107 |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 22396 | 55096 | 9639   | 51282 | 6359  | 507924 |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 37736 | 36765 | 15674  | 35778 | 15974 | 460201 |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 15723 | 46083 | 6388   | 44346 | 12225 | 458938 |
| [hashlru](https://npmjs.com/package/hashlru)                   | 29112 | 31696 | 12747  | 34130 | 12666 | 400039 |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 7313  | 30395 | 8547   | 25445 | 6398  | 273573 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 10655 | 20471 | 6796   | 19084 | 5244  | 211159 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 10395 | 20141 | 6662   | 18727 | 5417  | 208595 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 9790  | 20346 | 4652   | 17809 | 5180  | 200215 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 12547 | 16488 | 8921   | 16000 | 6002  | 193489 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 7605  | 17513 | 4121   | 15911 | 4558  | 174215 |
| [lru](https://www.npmjs.com/package/lru)                       | 11779 | 14194 | 5732   | 14914 | 4168  | 167282 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 8107  | 15373 | 7460   | 14296 | 3853  | 160538 |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 9195  | 11179 | 5258   | 15962 | 3995  | 156970 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 5218  | 12247 | 4380   | 10422 | 3341  | 120372 |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 4985  | 11534 | 4858   | 11001 | 2582  | 117345 |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 7027  | 9896  | 4308   | 8803  | 2876  | 106445 |

strint: stringified integer
| name                                                           | set   | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|-------|-------|--------|-------|-------|--------|
| [hashlru](https://npmjs.com/package/hashlru)                   | 42373 | 37383 | 14025  | 37383 | 13889 | 467280 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 18709 | 42105 | 7505   | 41322 | 17094 | 463318 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 18570 | 42373 | 7767   | 40984 | 16807 | 460981 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 16625 | 41408 | 7189   | 40486 | 16026 | 447223 |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 28050 | 42644 | 8120   | 40241 | 6020  | 423457 |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 26702 | 35273 | 11111  | 35273 | 14738 | 420389 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 20222 | 33389 | 10352  | 32787 | 17969 | 404743 |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 12895 | 36166 | 7933   | 36496 | 10995 | 379676 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 11587 | 36232 | 4918   | 36697 | 11461 | 377578 |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 23095 | 4836  | 8150   | 54795 | 6141  | 373528 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 10554 | 29197 | 7719   | 28777 | 7669  | 298648 |
| [lru](https://www.npmjs.com/package/lru)                       | 20964 | 28818 | 5132   | 27894 | 4749  | 296729 |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 7997  | 29240 | 5983   | 28249 | 5267  | 277277 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 6570  | 26774 | 5072   | 26385 | 6693  | 263924 |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 6037  | 22396 | 6244   | 20263 | 5520  | 214421 |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 8197  | 17668 | 6470   | 19436 | 6234  | 204218 |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 7496  | 15760 | 4614   | 13643 | 3716  | 153681 |

str: string that is not a number
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 7449 | 17637 | 7321   | 16260 | 5587  | 184365 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 6691 | 12788 | 5349   | 11396 | 3661  | 132380 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 6466 | 12821 | 3752   | 11409 | 3662  | 130502 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 6568 | 12547 | 5362   | 11142 | 3604  | 129869 |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 7095 | 12531 | 6250   | 10256 | 3142  | 125023 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 7278 | 10341 | 5919   | 9341  | 3801  | 117208 |
| [hashlru](https://npmjs.com/package/hashlru)                   | 9311 | 6517  | 4614   | 6307  | 8478  | 116712 |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 4241 | 9302  | 5745   | 8772  | 4632  | 109153 |
| [lru](https://www.npmjs.com/package/lru)                       | 6711 | 10449 | 5947   | 8937  | 2120  | 106001 |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 4379 | 9770  | 5583   | 9350  | 2702  | 103911 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 5259 | 9315  | 4915   | 9166  | 2539  | 101903 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 5302 | 8897  | 3049   | 8241  | 3269  | 97894  |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 4028 | 8214  | 3213   | 7339  | 2219  | 83701  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 3716 | 7321  | 3600   | 7110  | 2236  | 79725  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3512 | 7800  | 3361   | 6698  | 2057  | 77560  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 4660 | 6616  | 2740   | 4827  | 1910  | 65593  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 4360 | 5792  | 2826   | 5330  | 1956  | 65352  |

numstr: a mix of integers and strings that look like them
⠴ Benchmarking 1 of 17 caches [hashlru] failed correctness check at key="2"
⠧ Benchmarking 3 of 17 caches [hyperlru-object] failed correctness check at key="2"
⠋ Benchmarking 5 of 17 caches [lru] failed correctness check at key="2"
⠋ Benchmarking 11 of 17 caches [lru-fast] failed correctness check at key="2"
⠦ Benchmarking 13 of 17 caches [secondary-cache] failed correctness check at key="2"
⠹ Benchmarking 14 of 17 caches [simple-lru-cache] failed correctness check at key="2"
⠇ Benchmarking 15 of 17 caches [tiny-lru] failed correctness check at key="2"
⠼ Benchmarking 16 of 17 caches [mnemonist-object] failed correctness check at key="2"
| name                                                           | set   | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|-------|-------|--------|-------|-------|--------|
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 10309 | 18519 | 6470   | 16736 | 6105  | 196850 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 10194 | 18587 | 6112   | 16327 | 5863  | 193211 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 9281  | 18382 | 5215   | 16779 | 5757  | 191603 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 11211 | 17483 | 5025   | 15552 | 6085  | 188081 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 7257  | 13996 | 3567   | 13477 | 4880  | 151854 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 7070  | 13803 | 6260   | 12469 | 3387  | 141089 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 5044  | 12682 | 3731   | 10667 | 3192  | 121160 |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 4302  | 11461 | 3851   | 9901  | 2620  | 109443 |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 6510  | 9276  | 4511   | 8969  | 3217  | 106289 |
| [hashlru](https://npmjs.com/package/hashlru)                   | 0     | 0     | 0      | 0     | 0     | 0      |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 0     | 0     | 0      | 0     | 0     | 0      |
| [lru](https://www.npmjs.com/package/lru)                       | 0     | 0     | 0      | 0     | 0     | 0      |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 0     | 0     | 0      | 0     | 0     | 0      |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 0     | 0     | 0      | 0     | 0     | 0      |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 0     | 0     | 0      | 0     | 0     | 0      |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 0     | 0     | 0      | 0     | 0     | 0      |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 0     | 0     | 0      | 0     | 0     | 0      |

pi: multiples of pi
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 5588 | 11891 | 4519   | 10905 | 3064  | 121213 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 7457 | 9980  | 5838   | 9579  | 3842  | 117797 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 4700 | 10096 | 2950   | 11148 | 2719  | 111973 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 5372 | 10256 | 4248   | 10262 | 2951  | 111825 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 3807 | 8893  | 5237   | 8058  | 2400  | 91820  |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 3269 | 5313  | 3204   | 7968  | 2526  | 78151  |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 3309 | 6709  | 3230   | 6861  | 1837  | 73465  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3152 | 6234  | 3444   | 6246  | 1694  | 68150  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 2642 | 4103  | 2452   | 4190  | 1508  | 48535  |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 1643 | 2244  | 2016   | 2315  | 836   | 27789  |
| [lru](https://www.npmjs.com/package/lru)                       | 1688 | 1980  | 1744   | 1891  | 1277  | 26900  |
| [hashlru](https://npmjs.com/package/hashlru)                   | 1801 | 1599  | 1362   | 1545  | 1655  | 25761  |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 1358 | 1948  | 1803   | 1998  | 789   | 24298  |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 1326 | 1944  | 1590   | 1994  | 681   | 23449  |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 1542 | 1917  | 1484   | 1803  | 749   | 23079  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 1304 | 1755  | 1473   | 1871  | 663   | 22016  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 1336 | 1597  | 1162   | 1661  | 610   | 19980  |

float: floating point values
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 5420 | 10493 | 3197   | 12255 | 3091  | 122246 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 5478 | 11827 | 4633   | 10858 | 3048  | 120600 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 7582 | 10325 | 6209   | 9766  | 3849  | 120423 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 5318 | 8150  | 3664   | 11912 | 3293  | 114775 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 4004 | 8610  | 5488   | 8407  | 2555  | 94136  |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 3327 | 7067  | 3033   | 7776  | 2532  | 82428  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3077 | 6609  | 3506   | 6414  | 1681  | 69962  |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 3151 | 6279  | 3212   | 6623  | 1698  | 69956  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 2964 | 4551  | 2616   | 4665  | 1701  | 54027  |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 1657 | 2376  | 2028   | 2448  | 846   | 28940  |
| [lru](https://www.npmjs.com/package/lru)                       | 1749 | 2181  | 1821   | 1985  | 1207  | 27822  |
| [hashlru](https://npmjs.com/package/hashlru)                   | 1784 | 1675  | 1456   | 1604  | 1639  | 26264  |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 1662 | 2006  | 1612   | 1917  | 840   | 24739  |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 1367 | 2018  | 1788   | 2071  | 703   | 24446  |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 1368 | 1919  | 1880   | 1975  | 797   | 24233  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 1305 | 1866  | 1515   | 1886  | 684   | 22573  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 1323 | 1662  | 1232   | 1690  | 634   | 20484  |

obj: an object with a single key
⠴ Benchmarking 1 of 17 caches [hashlru] failed correctness check at key={"z":0}
⠧ Benchmarking 3 of 17 caches [hyperlru-object] failed correctness check at key={"z":0}
⠇ Benchmarking 5 of 17 caches [lru] failed correctness check at key={"z":0}
⠼ Benchmarking 11 of 17 caches [lru-fast] failed correctness check at key={"z":0}
⠋ Benchmarking 13 of 17 caches [secondary-cache] failed correctness check at key={"z":0}
⠴ Benchmarking 14 of 17 caches [simple-lru-cache] failed correctness check at key={"z":0}
⠙ Benchmarking 15 of 17 caches [tiny-lru] failed correctness check at key={"z":0}
⠧ Benchmarking 16 of 17 caches [mnemonist-object] failed correctness check at key={"z":0}
| name                                                           | set   | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|-------|-------|--------|-------|-------|--------|
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 10215 | 19822 | 6581   | 19157 | 5623  | 210377 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 9921  | 20429 | 6718   | 18349 | 5548  | 207332 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 8913  | 20387 | 5954   | 18639 | 5366  | 204966 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 11710 | 18100 | 5161   | 16273 | 5700  | 192746 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 7055  | 17227 | 3566   | 16064 | 4551  | 172432 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 7613  | 14286 | 6892   | 12723 | 3630  | 146741 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 5061  | 12158 | 4043   | 10655 | 3644  | 122134 |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 6129  | 10616 | 5444   | 10304 | 2957  | 115855 |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 4537  | 11056 | 3974   | 9128  | 2557  | 104641 |
| [hashlru](https://npmjs.com/package/hashlru)                   | 0     | 0     | 0      | 0     | 0     | 0      |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 0     | 0     | 0      | 0     | 0     | 0      |
| [lru](https://www.npmjs.com/package/lru)                       | 0     | 0     | 0      | 0     | 0     | 0      |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 0     | 0     | 0      | 0     | 0     | 0      |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 0     | 0     | 0      | 0     | 0     | 0      |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 0     | 0     | 0      | 0     | 0     | 0      |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 0     | 0     | 0      | 0     | 0     | 0      |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 0     | 0     | 0      | 0     | 0     | 0      |

rand: random floating point number
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 4912 | 10644 | 3218   | 11744 | 3027  | 118829 |
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 5789 | 11013 | 4197   | 10834 | 3099  | 118479 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 7524 | 10050 | 5936   | 9398  | 3826  | 117254 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 5640 | 9217  | 3837   | 10846 | 3061  | 112303 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 3982 | 8052  | 5155   | 8651  | 2431  | 92685  |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 3176 | 7246  | 2881   | 7070  | 2488  | 78761  |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 3071 | 6810  | 3150   | 6481  | 1812  | 71187  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3175 | 6295  | 3386   | 6109  | 1712  | 67726  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 3341 | 4206  | 2594   | 4619  | 1653  | 53254  |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 1669 | 2380  | 1984   | 2350  | 859   | 28507  |
| [lru](https://www.npmjs.com/package/lru)                       | 1723 | 1866  | 1668   | 1829  | 1265  | 26182  |
| [hashlru](https://npmjs.com/package/hashlru)                   | 1790 | 1610  | 1402   | 1546  | 1613  | 25607  |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 1667 | 2060  | 1572   | 1946  | 809   | 24861  |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 1368 | 1958  | 1791   | 1999  | 768   | 24236  |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 1360 | 1952  | 1760   | 1987  | 696   | 23751  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 1205 | 1815  | 1509   | 1949  | 682   | 22519  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 1391 | 1665  | 1217   | 1740  | 645   | 20919  |

sym: a Symbol object
⠼ Benchmarking 5 of 17 caches [lru] failed correctness check TypeError: Cannot convert a Symbol value to a string
    at LRU.set (/Users/isaacs/dev/isaacs/lru-cache/bench-lru/node_modules/lru/index.js:69:41)
    at self.onmessage (evalmachine.<anonymous>:116:38)
    at process.<anonymous> (/Users/isaacs/dev/isaacs/lru-cache/bench-lru/node_modules/tiny-worker/lib/worker.js:60:55)
    at process.emit (node:events:520:28)
    at emit (node:internal/child_process:936:14)
    at processTicksAndRejections (node:internal/process/task_queues:84:21)
| name                                                           | set   | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|-------|-------|--------|-------|-------|--------|
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 9886  | 19361 | 6991   | 17809 | 5445  | 201116 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 9809  | 19455 | 6258   | 17794 | 5430  | 200361 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 9074  | 19417 | 6450   | 17953 | 5359  | 199409 |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 7776  | 20492 | 6831   | 17391 | 5593  | 198779 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 10893 | 17652 | 5375   | 15540 | 5616  | 185897 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 7297  | 14399 | 6925   | 12650 | 3591  | 145921 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 7174  | 14124 | 3938   | 12300 | 4535  | 144833 |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 7758  | 12845 | 6824   | 11682 | 3125  | 134910 |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 6028  | 3537  | 6916   | 16340 | 2874  | 125653 |
| [hashlru](https://npmjs.com/package/hashlru)                   | 9602  | 7148  | 5144   | 6761  | 8264  | 120917 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 5179  | 12114 | 3814   | 10846 | 3207  | 120779 |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 4636  | 8957  | 6044   | 8981  | 4601  | 110097 |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 4540  | 10959 | 4344   | 8799  | 2696  | 103776 |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 6129  | 8421  | 5045   | 8460  | 2817  | 98951  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 3577  | 7533  | 3856   | 6349  | 2258  | 76644  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 5319  | 7573  | 3177   | 5238  | 2055  | 72999  |
| [lru](https://www.npmjs.com/package/lru)                       | 0     | 0     | 0      | 0     | 0     | 0      |

longstr: a very long string
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 5882 | 11044 | 5009   | 10147 | 3107  | 116175 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 5828 | 11287 | 4102   | 10320 | 2738  | 114909 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 5936 | 9960  | 4827   | 10020 | 3224  | 112799 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 6464 | 9264  | 6291   | 8396  | 3193  | 104956 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 4900 | 8834  | 3499   | 8094  | 2759  | 94066  |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 4700 | 8316  | 5185   | 7997  | 2298  | 91008  |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 3666 | 7862  | 3514   | 6991  | 2044  | 79607  |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 2949 | 6658  | 4930   | 6640  | 2690  | 77452  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3377 | 7283  | 3492   | 6607  | 1856  | 74410  |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 2248 | 4006  | 4218   | 3946  | 2547  | 53197  |
| [hashlru](https://npmjs.com/package/hashlru)                   | 4003 | 3281  | 2791   | 3078  | 3169  | 51875  |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 2261 | 4432  | 3907   | 4352  | 1616  | 51565  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 3132 | 4287  | 2691   | 4307  | 1282  | 49761  |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 2502 | 3859  | 3854   | 3752  | 1826  | 48325  |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 1989 | 3715  | 2690   | 3430  | 1235  | 41138  |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 2500 | 3394  | 2086   | 2845  | 1148  | 37233  |
| [lru](https://www.npmjs.com/package/lru)                       | 2345 | 3073  | 2714   | 2903  | 1042  | 36348  |

mix: a mix of all the types
⠦ Benchmarking 1 of 17 caches [hashlru] failed correctness check at key={"z":3}
⠧ Benchmarking 3 of 17 caches [hyperlru-object] failed correctness check at key={"z":3}
⠏ Benchmarking 5 of 17 caches [lru] failed correctness check TypeError: Cannot convert a Symbol value to a string
    at LRU.set (/Users/isaacs/dev/isaacs/lru-cache/bench-lru/node_modules/lru/index.js:69:41)
    at self.onmessage (evalmachine.<anonymous>:116:38)
    at process.<anonymous> (/Users/isaacs/dev/isaacs/lru-cache/bench-lru/node_modules/tiny-worker/lib/worker.js:60:55)
    at process.emit (node:events:520:28)
    at emit (node:internal/child_process:936:14)
    at processTicksAndRejections (node:internal/process/task_queues:84:21)
⠼ Benchmarking 11 of 17 caches [lru-fast] failed correctness check at key={"z":3}
⠴ Benchmarking 13 of 17 caches [secondary-cache] failed correctness check at key={"z":3}
⠙ Benchmarking 14 of 17 caches [simple-lru-cache] failed correctness check at key={"z":3}
⠧ Benchmarking 15 of 17 caches [tiny-lru] failed correctness check at key={"z":3}
⠸ Benchmarking 16 of 17 caches [mnemonist-object] failed correctness check at key={"z":3}
| name                                                           | set  | get1  | update | get2  | evict | score  |
|----------------------------------------------------------------|------|-------|--------|-------|-------|--------|
| [lru-cache-7](https://npmjs.com/package/lru-cache)             | 7457 | 13342 | 5802   | 12195 | 3979  | 141612 |
| [mnemonist-map](https://www.npmjs.com/package/mnemonist)       | 8061 | 14015 | 6369   | 11312 | 3975  | 140971 |
| [lru-cache-7-dispose](https://npmjs.com/package/lru-cache)     | 7138 | 13271 | 5321   | 12210 | 3953  | 140225 |
| [lru-cache-7-size](https://npmjs.com/package/lru-cache)        | 6847 | 13405 | 4351   | 12070 | 3757  | 137395 |
| [js-lru](https://www.npmjs.com/package/js-lru)                 | 5316 | 9676  | 4381   | 9170  | 2900  | 104391 |
| [lru-cache-7-ttl](https://npmjs.com/package/lru-cache)         | 5708 | 9833  | 3164   | 8333  | 3419  | 102839 |
| [lru-cache](https://npmjs.com/package/lru-cache)               | 4165 | 8624  | 3328   | 7890  | 2557  | 89765  |
| [hyperlru-map](https://npmjs.com/package/hyperlru-map)         | 3875 | 7758  | 3351   | 7179  | 2017  | 80355  |
| [modern-lru](https://npmjs.com/package/modern-lru)             | 4919 | 6256  | 3227   | 6129  | 2147  | 73213  |
| [hashlru](https://npmjs.com/package/hashlru)                   | 0    | 0     | 0      | 0     | 0     | 0      |
| [hyperlru-object](https://npmjs.com/package/hyperlru-object)   | 0    | 0     | 0      | 0     | 0     | 0      |
| [lru](https://www.npmjs.com/package/lru)                       | 0    | 0     | 0      | 0     | 0     | 0      |
| [lru-fast](https://npmjs.com/package/lru-fast)                 | 0    | 0     | 0      | 0     | 0     | 0      |
| [secondary-cache](https://npmjs.com/package/secondary-cache)   | 0    | 0     | 0      | 0     | 0     | 0      |
| [simple-lru-cache](https://npmjs.com/package/simple-lru-cache) | 0    | 0     | 0      | 0     | 0     | 0      |
| [tiny-lru](https://npmjs.com/package/tiny-lru)                 | 0    | 0     | 0      | 0     | 0     | 0      |
| [mnemonist-object](https://www.npmjs.com/package/mnemonist)    | 0    | 0     | 0      | 0     | 0     | 0      |

The best performers are lru-cache version 7 and mnemonist's LRUMap, across most categories. mnemonist-map seems to consistently have slightly better eviction and set performance, and slightly worse get performance, for many key types. The difference is small enough to be negligible, which is to be expected.

For object-friendly key spaces (strictly integers or strictly short strings), mnemonist's LRUCache and hashlru seem to do the best.

For strictly integer key sets, lru-fast lives up to its name, blowing the other implementations out of the water, but did not perform nearly as well with other types of keys.

---

What follows below is Dominic Tarr's original discussion from 2016.

@isaacs

---

Introduction

An LRU cache is a cache with bounded memory use. The point of a cache is to improve performance, so how performant are the available implementations?

LRUs achive bounded memory use by removing the oldest items when a threashold number of items is reached. We measure 3 cases, adding an item, updating an item, and adding items which push other items out of the LRU.

There is a previous benchmark 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)

Benchmark

I run a very simple multi-process benchmark, with 5 iterations to get a median of ops/ms:

1. Set the LRU to fit max N=200,000 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.

Results

Operations per millisecond (higher is better):

name	set	get1	update	get2	evict
hashlru	18536	17590	17794	18332	9381
mnemonist-object	15314	69444	35026	68966	7949
quick-lru	8214	4572	6777	4608	6345
tiny-lru	6530	46296	37244	42017	5961
lru-fast	5979	36832	32626	40900	5929
mnemonist-map	6272	15785	10923	16077	3738
lru	3927	5454	5001	5366	2827
simple-lru-cache	3393	3855	3701	3899	2496
hyperlru-object	3515	3953	4044	4102	2495
js-lru	3813	10010	9246	10309	1843
secondary-cache	2780	5705	5790	10549	1727
lru-cache	2275	3388	3334	3301	1593
hyperlru-map	2424	2508	2443	2540	1552
modern-lru	2710	3946	3581	4021	1327
mkc	1559	2044	1178	2161	1037

We can group the results in a few categories:

• all rounders (mnemonist, lru_cache, tiny-lru, simple-lru-cache, lru-fast) where the performance to add update and evict are comparable.
• fast-write, slow-evict (lru, hashlru, lru-native, modern-lru) these have better set/update times, but for some reason are quite slow to evict items!
• slow in at least 2 categories (lru-cache, mkc, faster-lru-cache, secondary-cache)

Discussion

It appears that all-round performance is the most difficult to achive, in particular, performance on eviction is difficult to achive. I think eviction performance is the most important consideration, because once the cache is warm each subsequent addition causes an eviction, and actively used, hot, cache will run close to it's eviction performance. Also, some have faster add than update, and some faster update than add.

modern-lru gets pretty close to lru-native perf. I wrote hashlru after my seeing the other results from this benchmark, it's important to point out that it does not use the classic LRU algorithm, but has the important properties of the LRU (bounded memory use and O(1) time complexity)

Splitting the benchmark into multiple processes helps minimize JIT state pollution (gc, turbofan opt/deopt, etc.), and we see a much clearer picture of performance per library.

Future work

This is still pretty 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.

Conclusion

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 LRU implementation I realized that something far simpler could do the same job. Especially given the strengths and weaknesses of javascript, this is significantly faster than any of the other implementations, including the C implementation. Likely, the overhead of the C<->js boundry is partly to blame here.

License

MIT