feat(cache): enable lru cache #158
Conversation
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Benchmark result:
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By updating the stat code to let num = 0;
const stat = new Set();
// ...
num++;
stat.add(input);
console.log(num, stat.size);And here is the result of one generation of a hexo dummy site (hexo-theme-unit):
And for my own blogs:
It shows why we definitely need a cache. |
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@SukkaW I have some questions.
const LFU = require('node-lfu-cache');
const cache = new LFU(2);
cache.set(1, 1);
cache.set(2, 2);
cache.get(1); // returns 1
cache.set(3, 3); // evicts key 2
cache.get(2); // returns undefined (not found)
cache.get(3); // returns 3.
cache.set(4, 4); // evicts key 1.
cache.get(1); // returns undefined (not found)
cache.get(3); // returns 3
cache.get(4); // returns 4The expected result should be like comments. (https://leetcode.com/problems/lfu-cache/) cache.get(1); // returns 1
cache.get(3); // returns 3
cache.get(4); // returns undefined (not found)This means that when the cache is full, no more items can be added to the cache.
cache.set(1, v);
cache.get(1);
cache.set(2, v);
cache.get(2);
...
cache.set(n, v);
cache.get(n);
// cache evicts key 1, 2 ...
...
cache.set(1, v);
cache.get(1);
cache.set(2, v);
cache.get(2);
...
cache.set(n, v);
cache.get(n);
// cache evicts key 1, 2 ...
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We all want to better utilize the cache and not to fill up with once-called key-value, right? Also, the code case you given is exactly expected
I have provided a stat in my last comment:
Although there are 944 urls being processed by |
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Ok, I understand your meaning.
This is not working. See my test code above. Or you can run this test. I have tested using your branch of hexo-utils and confirmed about that. |
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@dailyrandomphoto Maybe not I have setup a PoC of LFU cache: const LFU = require('node-lfu-cache');
const cache = new LFU(50);
const random = (min, max) => Math.round(Math.random() * (max - min)) + min;
const cacheFunc = (key, value) => {
if (cache.has(key)) return cache.get(key);
cache.set(key, value);
return value;
}
// Will be called only once
cacheFunc('cold', '123');
// Will be called for 10 times
for (let i = 1; i <= 10; i++) {
cacheFunc('hot', '456');
}
// Let the cache size limit exceeded
for (let i = 1; i <= 60; i++) {
cacheFunc(String(100 + i), random(100, 900));
}
console.log('Cold: ' + cacheFunc('cold', '789'));
// Should be 789 not 123, because the cold cache will be removed from the cache.
console.log('Hot: ' + cacheFunc('hot', '789'));
// Should be 456 not 789, because it is hot and remains in the cache.
// > "Cold: 789"
// > "Hot: 456" |
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This is a good example. const LFU = require('node-lfu-cache');
const cache = new LFU(50);
const random = (min, max) => Math.round(Math.random() * (max - min)) + min;
const cacheFunc = (key, value) => {
if (cache.has(key)) return cache.get(key);
cache.set(key, value);
return value;
}
// Will be called only once
cacheFunc('cold', '123');
// Will be called for 10 times
for (let i = 1; i <= 10; i++) {
cacheFunc('hot', '456');
}
// Let the cache size limit exceeded
for (let i = 1; i <= 60; i++) {
// save to cache
cacheFunc(String(100 + i), random(100, 900));
// read from cache
cacheFunc(String(100 + i), random(100, 900));
}
cacheFunc('new', '123');
console.log('Cold: ' + cacheFunc('cold', '789'));
// Should be 789 not 123, because the cold cache will be removed from the cache.
console.log('Hot: ' + cacheFunc('hot', '789'));
// Should be 456 not 789, because it is hot and remains in the cache.
console.log('New: ' + cacheFunc('new', '789'));
// Should be 123 not 789, because it is a new item.
// You will find that, when the cache is full, no more items can be added to the cache.
console.log(cache.dump());https://runkit.com/dailyrandomphoto/5df84e2da91f66001d9620c5 console.log('New: ' + cacheFunc('new', '789'));
// Should be 123 not 789, because it is a new item.BUT, it shows |
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I tasted this patch with a large blog (which has dummy 3000 posts). The result shows:
Could you consider to use a plain object? Detals:I have a dummy blog which has 3000 posts. I run And also, to follow @dailyrandomphoto 's comment #158 (comment) Source code:
Result:Elapsed time:
Counter:
Environment:
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@seaoak What about memory usage? I am still wondering if we need a LFU cache. |
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@seaoak The performance regression in your benchmark should be caused by the issue of |
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@dailyrandomphoto @seaoak I have change LFU to LRU, please feel free to have a benchmark see if any performance gained. |
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Should be superseded by #162, |
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I'm sorry I'm late. I found a tool "memwatch". The result shows using cache has little effect to memory usage. Details:For each condition, measure 10 times and calculate the average. Condition changes:
Result:
(modified: data of "seaoak" was mistook) |
I'm guessing cache only stores the pointer to the value, rather than the actual value. |
I have setup a stat by adding a few line of the code to
node_modules/hexoin my local dummy site:It turns out that even as few as 17 posts in hexo-theme-unit-test,
full_url_for()helper will be called for 537 times andisExternalLink()will be called for 2599 times in one generation!So I bring up this PR. The
node-lfu-cacheis enabled for those functions: