Bug #20184
closedRuby segfaults on Fly.io with 256 MB RAM
Description
I've been running a Ruby 3.2 app on Fly.io with 256 MB RAM and it has been working fine.
When I upgraded to Ruby 3.3.0, any Ruby script would crash immediately with a segfault.
I haven't been able to reproduce it outside of fly.io.
I created a repository with a basic rack app which crashes on fly.io.
The readme includes the full output and a GDB backtrace.
https://github.com/aalin/ruby-3-3-0-fly-crash
Updated by nobu (Nobuyoshi Nakada) 10 months ago
In shape.c:Init_default_shapes(), the result of mmap
for rb_shape_tree_ptr->shape_cache
seems unchecked.
I'm not sure if it can continue without shape_cache
.
Updated by nobu (Nobuyoshi Nakada) 10 months ago
- Status changed from Open to Closed
- Backport changed from 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN to 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED
8b8dcc7af174def5216044019c1d3e42edfdc7cf should have fixed this.
Updated by ioquatix (Samuel Williams) 10 months ago
I was also investigating this issue.
On low-memory systems (< ~400MB RAM+Swap), Init_default_shapes
will fail and cause Ruby to segfault later.
Even something as simple as ruby -e "puts 123"
will fail.
The 2nd mmap
in shape.c
tries to allocate 384MB as a cache. This fails with MAP_FAILED
which is stored into a shape_cache
pointer and later this pointer is derefenced causing a segfault.
The current merged fix skips the cache if the mmap
fails, but might I suggest we explore the following:
- Divide and conquer strategy for finding an allocation size that works (e.g. divide by half and try again a few times).
- Expose an environment variable to control the size, so that those on memory constrained systems can at least enable a smaller cache.
Updated by ioquatix (Samuel Williams) 10 months ago
I also wonder if we should add some CI for running ruby on a low memory/virtual memory constrained system.
Updated by anton-stepanof (Anton Stepanov) 9 months ago
Backport PR for 3.3: https://github.com/ruby/ruby/pull/9805
Updated by mame (Yusuke Endoh) 9 months ago
- Has duplicate Bug #20263: Backport https://github.com/ruby/ruby/pull/9498 to Ruby 3.3 added
Updated by naruse (Yui NARUSE) 8 months ago
- Backport changed from 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED to 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONE
ruby_3_3 53f0c5a4e8834f11af0f903d2c59754d9be2a7f2.