Question regarding cache eviction

[juyoungbang]

Hi.
I'm currently looking into the caching mechanism of Sherman and came up with some questions.

First of all, I have been trying to adjust the amount of index cache used by Sherman
and found that it can be done by changing kIndexCacheSize in Sherman/include/Common.h.
Just to verify, is it the right way to adjust the amount of index cache?

In addition, I also have a question regarding the cache eviction code.
In the get_a_random_entry function, k is selected through the following random function.

auto k = rand_r(&seed) % (1000ull * define::MB);

What I have understood is that, a random key between 0 and 1000ull * define::MB will be selected.
Then it will try to find a cached page which includes the given key range and evict the found page.
My question here is, what if there is no page left which includes the key range between 0 and 1000ull * define::MB?
Will it fail to find a page to evict and fall into a infinite loop (since it continuously retries) ?

[Transpeptidase]

Hi.

1. changing kIndexCacheSize can adjust the size of index cache
2. (1000ull * define::MB) should be the range of keys.

[juyoungbang]

Thanks.

However, I've encountered one more problem.
The data type of the keys I am using is uint64_t and are quite large values.
But it seems that rand_r is a function returning a integer random number.
So I think it's failing to generate a number in the range of my keys.

Will it be okay to use any other random functions or do you recommend other solutions?

[Transpeptidase]

Yes, you can use any other random functions, and our goal is to use power-of-two to evict a node in the cache.

[juyoungbang]

Thanks a lot:)
I'll close the issue.