fix(cli): configure v8 isolate with cgroups-constrained memory limit

[magurotuna]

This change configures V8 isolates to respect memory limits imposed by cgroups on Linux.

It adds support for detecting both cgroups v1 and v2 memory limits, enabling Deno to properly adapt to containerized environments with memory constraints. When cgroups information is unavailable or not applicable, it falls back to using the system's total memory as before.

Closes #29077

Test

For testing, I created a ubuntu VM with 1Gi memory. Within this VM, set up a cgroup with 512Mi memory limit, then ran the following script to see how much heap size limit the V8 isolate had.

import * as v8 from "node:v8";

console.log(v8.getHeapStatistics());

Ubuntu 20.04

In this version of ubuntu, hybrid mode is enabled by default.

$ cat /proc/self/cgroup
12:rdma:/
11:blkio:/user.slice
10:devices:/user.slice
9:cpu,cpuacct:/user.slice
8:pids:/user.slice/user-1000.slice/session-3.scope
7:memory:/user.slice/user-1000.slice/session-3.scope
6:perf_event:/
5:freezer:/
4:net_cls,net_prio:/
3:hugetlb:/
2:cpuset:/
1:name=systemd:/user.slice/user-1000.slice/session-3.scope
0::/user.slice/user-1000.slice/session-3.scope

Create a new cgroup with 512Mi memory limit and run the above script in this cgroup:

$ sudo cgcreate -g memory:/mygroup
$ sudo cgset -r memory.limit_in_bytes=$((512 * 1024 * 1024)) mygroup
$ sudo cgexec -g memory:mygroup ./deno run main.mjs
{
  total_heap_size: 7745536,
  total_heap_size_executable: 0,
  total_physical_size: 7090176,
  total_available_size: 266348216,
  used_heap_size: 6276752,
  heap_size_limit: 271581184,
  malloced_memory: 303200,
  peak_malloced_memory: 140456,
  does_zap_garbage: 0,
  number_of_native_contexts: 1,
  number_of_detached_contexts: 0,
  total_global_handles_size: 24576,
  used_global_handles_size: 22432,
  external_memory: 3232012
}

This indicates that the isolate was informed of cgroup-constrained memory limit (512Mi) and hence got ~270M heap limit.

Ubuntu 22.04

In this version of ubuntu, cgroup v2 is used.

$ cat /proc/self/cgroup
0::/user.slice/user-1000.slice/session-3.scope

Run the above script using systemd-run:

$ sudo systemd-run --property=MemoryMax=512M --pty bash -c '/home/ubuntu/deno run /home/ubuntu/main.mjs'
{
  total_heap_size: 7745536,
  total_heap_size_executable: 0,
  total_physical_size: 7090176,
  total_available_size: 266348184,
  used_heap_size: 6276784,
  heap_size_limit: 271581184,
  malloced_memory: 303200,
  peak_malloced_memory: 140456,
  does_zap_garbage: 0,
  number_of_native_contexts: 1,
  number_of_detached_contexts: 0,
  total_global_handles_size: 24576,
  used_global_handles_size: 22432,
  external_memory: 3232012
}

Again the isolate got ~270M heap limit properly.
Note that it should have had bigger heap limit if the entire system memory, i.e. 1Gi, had been passed to V8. In fact, if we run the same script outside the cgroup, it does display larger heap_size_limit like below:

$ ./deno run main.mjs
{
  total_heap_size: 7745536,
  total_heap_size_executable: 0,
  total_physical_size: 7090176,
  total_available_size: 546580152,
  used_heap_size: 6276752,
  heap_size_limit: 551813120,
  malloced_memory: 303200,
  peak_malloced_memory: 140456,
  does_zap_garbage: 0,
  number_of_native_contexts: 1,
  number_of_detached_contexts: 0,
  total_global_handles_size: 24576,
  used_global_handles_size: 22432,
  external_memory: 3232012
}

[Copilot]

Pull Request Overview

This PR configures V8 isolates to honor memory limits imposed by cgroups on Linux by detecting cgroup v1 and v2 configurations. Key changes include:

• Adding a new Linux-specific logic branch in create_isolate_create_params to use cgroup memory limits.
• Introducing a helper module with functions to parse /proc/self/cgroup and determine the correct memory limit.
• Including tests to validate the cgroup parsing function for both v1 and v2 (and hybrid mode).

[devsnek]

generally seems good, I am curious though if there's some crate for parsing the cgroups instead of manually implementing it.

[littledivy]

Is there any impact on startup perf? Can we this be feature flagged at compile/runtime instead?

[bartlomieju]

Is there any impact on startup perf? Can we this be feature flagged at compile/runtime instead?

That's a good point, it won't be used in 99% cases - maybe enable it only via env var

[magurotuna]

I am curious though if there's some crate for parsing the cgroups instead of manually implementing it.

Looks like this crate https://docs.rs/cgroups-rs/0.3.4/cgroups_rs/index.html provides what we want. I'll replace the manual implementation with it.

maybe enable it only via env var

OK, let's do that