why memory.usage read from file but not compute from stats.

[zdyj3170101136]

in containerv1, read memory stats from file memory.stats, read memory usage from file memory.usage_in_bytes.

why do not compute memory usage from memory.stats[rss] + memory.stats[cache]?

it there have any difference between value with memory.usage_in_bytes and memory.stats[rss] + memory.stats[cache]?

[cyphar]

They measure different things. memory.usage_in_bytes in cgroupv1 and memory.usage in cgroupv2 account for all system memory usage by processes in the cgroups, which includes shmem files, dirty pages, writeback, etc. None of these are accounted for in rss and cache (or the cgroupv2 equivalents) -- if you look at runc events --stat of most containers, rss+cache will be smaller than the usage reported by the kernel.

As for why we read them from the file, it's because we just provide the information the kernel gives you. It's up to the user as to what information they need -- if they need rss+cache they can calculate that themselves from the stats we provide.