Default cache size documentation problem

[FranciscoPombal]

Please provide the following information

libtorrent version (or branch): RC_1_2

platform/architecture: N/A

compiler and compiler version: N/A

please describe what symptom you see, what you would expect to see instead and
how to reproduce it.

Related to qbittorrent/qBittorrent#12336.

The table in the documentation says (number of 16 KiB blocks):

name	type	default
cache_size	int	2048

but in the code:

• m_max_use is initialized like this to 64
• if the amount of physical RAM cannot be determined, it is set to 1024 (the documentation text also states this further down):

  If the amount of physical RAM cannot be determined, it's set to 1024 (= 16 MiB).

In neither case does it default to 2048.

[arvidn]

The logic to set the cache size based on the amount of physical RAM is only triggered if settings_pack::cache_size is -1, right? and that's not default.

I don't see a code path where m_max_use is left as its initialized value of 64. In the disk_io_thread constructor, settings_updated() is called, specifically to trigger the initial value of m_max_use. It will in turn call block_cache::set_settings() which will call disk_buffer_pool::set_settings() which does this initialization.

As far as I can tell, m_max_use is indeed set to 2048 by default.

[arvidn]

I see, the qbt ticket is specifically about the auto case. I agree that the 1024 there should at least be the same as the regular default.

[arvidn]

@FranciscoPombal is there any action I should take on this ticket still?

[FranciscoPombal]

@arvidn
I think everything has been addressed, thanks. Relevant commit for future reference: 6c88015