used / available / free memory is wrong on Linux

[srid]

Describe the bug

My environment,

• sysinfo.version = "0.29.10"
• 13th Gen Intel(R) Core(TM) i9-13900 (Hetzner Dedicated server)
• rustc 1.73.0-nightly (32303b219 2023-07-29)

The following Rust code,

        println!(
            "Memory used / free / available / total => {} / {} / {} / {}",
            bytes_human_readable(sys.used_memory()),
            bytes_human_readable(sys.free_memory()),
            bytes_human_readable(sys.available_memory()),
            bytes_human_readable(sys.total_memory())
        );

outputs:

Memory used / free / available / total => 55 GB / 6 GB / 6 GB / 62 GB

Note that both free and available are detected as 6GB, which is wrong. The correct values are reported by the free command:

❯ free -m
               total        used        free      shared  buff/cache   available
Mem:           64058       13762        1670          17       48624       49565
Swap:              0           0           0

To Reproduce

https://github.com/juspay/nix-browser/compare/2a2e72fc6aafba640b94bc18d418377716a240e7..2a7404807db29bd1005ef1d5b2be62a800dac791

[srid]

/proc/meminfo

❯ cat /proc/meminfo
MemTotal:       65595448 kB
MemFree:         1709008 kB
MemAvailable:   50753656 kB
Buffers:         3273820 kB
Cached:         42092296 kB
SwapCached:            0 kB
Active:         19315980 kB
Inactive:       39329500 kB
Active(anon):   13258948 kB
Inactive(anon):    38612 kB
Active(file):    6057032 kB
Inactive(file): 39290888 kB
Unevictable:       10496 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Zswap:                 0 kB
Zswapped:              0 kB
Dirty:                76 kB
Writeback:             0 kB
AnonPages:      13281840 kB
Mapped:           380944 kB
Shmem:             18152 kB
KReclaimable:    4426336 kB
Slab:            4957284 kB
SReclaimable:    4426336 kB
SUnreclaim:       530948 kB
KernelStack:       13068 kB
PageTables:        35988 kB
SecPageTables:         0 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    32797724 kB
Committed_AS:   17006928 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       46716 kB
VmallocChunk:          0 kB
Percpu:            32768 kB
AnonHugePages:     45056 kB
ShmemHugePages:     8192 kB
ShmemPmdMapped:        0 kB
FileHugePages:         0 kB
FilePmdMapped:         0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB
DirectMap4k:      304756 kB
DirectMap2M:     5722112 kB
DirectMap1G:    60817408 kB

[GuillaumeGomez]

What does htop display?

[srid]

htop is in accord with free -m, thus behaves correctly. Do you need any diagnostic info aside from the /proc/meminfo pasted above?

[GuillaumeGomez]

No, I think I have all needed. You can also check what's wrong yourself, which would be much faster than waiting for me as I'm a super busy lately... The code which gets this information is in https://github.com/GuillaumeGomez/sysinfo/blob/0.29/src/linux/system.rs#L252. If you could check what is done wrong, it'd be really helpful (sending a fix would be the best! :D)

[Treasure-u]

I also meet this problem and I think if we want to get used / avialble / free memory like command "free -h",maybe we should not use the part of cgroups to sub our memory (https://docs.rs/sysinfo/0.29.10/src/sysinfo/linux/system.rs.html#286-318)

[GuillaumeGomez]

I'm really confused about this cgroup thing. Maybe there is a way to figure out when to use it or not...

[Treasure-u]

After looking at the sysinfo source code, I found that it seems that cgroups are only considered in the memory part, in fact, the /proc/meminfo data does not need to consider cgroups, I hope my answer is correct and helpful to you :)

[GuillaumeGomez]

I'm investigating this issue again. @srid, can you provide me the content of the following files please:

/sys/fs/cgroup/memory.current
/sys/fs/cgroup/memory.max
/sys/fs/cgroup/memory/memory.usage_in_bytes
/sys/fs/cgroup/memory/memory.limit_in_bytes

[GuillaumeGomez]

In the meantime, I decided to move the cgroup limits computation into its own function so it can be queried separately in #1119.