BEAM VM consumes big amounts of memory VIRT vs :erlang.memory(:total)

Does that reply by one of Erlang’s maintainers help?

App is not in a container.

In vm.args:

+P 1024 - max processes 1024
+Q 1024 - max ports 1024

Both does not help.

Still the same 4G.

OS: Debian 10.
Elixir 1.15.
Erlang 26.0.2.

Did you read the BEAM VM option he linked to? This is not about containers, it’s an option that should work regardless of where the app is started.

ERL_MAX_PORTS does not help.

I just tired +MIscs +MIscs 128 and mem usage dropped to 3188MB.

Hm, seems there is more that can be done but I am not aware of it, sorry.

Wonder if @garazdawi would be willing to help further.

I would use recon_alloc — recon v2.5.3 to get a view of what is using memory. Especially recon_alloc:fragmentation/1 can be helpful to look at.

If you can provide a recon_alloc snapshot I can see if I can figure out what is using all the extra virtual memory.

Here is my recon_alloc snapshot: https://drive.google.com/file/d/1E5dCvdoug2DtPIl3P0dCM2DNU6lzx30o/view

The statistics for the Erlang allocators do not indicate that you are using a lot of virtual memory. What does :erlang.system_info({:allocator,:erts_mmap}) return?

[
  default_mmap: [options: [scs: 0], os: [sizes: [used: 29888512]]],
  literal_mmap: [
    options: [scs: 1073676288, sco: true, scrpm: false, scrfsd: 1024],
    supercarrier: [
      sizes: [
        total: 1073741824,
        total_sa: 4096000,
        total_sua: 0,
        used: 4161536,
        used_sa: 4096000,
        used_sua: 0
      ],
      free_segs: [
        used: 0,
        max: 0,
        allocated: 0,
        reserved: 1024,
        used_sa: 0,
        used_sua: 0
      ]
    ]
  ]
]

Summary from /proc/16025/smaps where 16025 - beam pid.

* Mem usage for PID 16025
-- Size: 4172764 kB
-- Rss: 135352 kB
-- Pss: 113538 kB
Shared Clean 5440 kB
Shared Dirty 34504 kB
Private 95412 kB

Some very strange region

VmFlags: rd wr mr mw me ac sd
7f659a834000-7f65da43b000 ---p 00000000 00:00 0
Size:            1044508 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:    1
ProtectionKey:         0

And many empty regions with the size 65504 kB

VmFlags: rd wr mr mw me nr sd
7f6530008000-7f6534000000 ---p 00000000 00:00 0
Size:              65504 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Rss:                   0 kB
Pss:                   0 kB
Shared_Clean:          0 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:            0 kB
Anonymous:             0 kB
LazyFree:              0 kB
AnonHugePages:         0 kB
ShmemPmdMapped:        0 kB
Shared_Hugetlb:        0 kB
Private_Hugetlb:       0 kB
Swap:                  0 kB
SwapPss:               0 kB
Locked:                0 kB
THPeligible:    1
ProtectionKey:         0

My script for summary:

#!/bin/bash

pid=$1

echo "* Mem usage for PID $pid"
sz=$(awk 'BEGIN {i=0} /^Size/ {i = i + $2} END {print i}' /proc/$pid/smaps)
rss=$(awk 'BEGIN {i=0} /^Rss/ {i = i + $2} END {print i}' /proc/$pid/smaps)
pss=$(awk 'BEGIN {i=0} /^Pss/ {i = i + $2 + 0.5} END {print i}' /proc/$pid/smaps)
sc=$(awk 'BEGIN {i=0} /^Shared_Clean/ {i = i + $2} END {print i}' /proc/$pid/smaps)
sd=$(awk 'BEGIN {i=0} /^Shared_Dirty/ {i = i + $2} END {print i}' /proc/$pid/smaps)
pc=$(awk 'BEGIN {i=0} /^Private_Clean/ {i = i + $2} END {print i}' /proc/$pid/smaps)
pd=$(awk 'BEGIN {i=0} /^Private_Dirty/ {i = i + $2} END {print i}' /proc/$pid/smaps)
echo "-- Size: $sz kB"
echo "-- Rss: $rss kB"
echo "-- Pss: $pss kB"
echo "Shared Clean $sc kB"
echo "Shared Dirty $sd kB"
echo "Private $(($pd + $pc)) kB"