Issue #21042 has been updated by Eregon (Benoit Daloze). On JVM there is [`ThreadMXBean#getThreadAllocatedBytes`](https://docs.oracle.com/en/java/javase/11/docs/api/jdk.management/com/sun/ma...)). There is no way on JVM to know the number of objects allocated, only bytes. So this means TruffleRuby and JRuby could implement `Thread.current.total_allocated_bytes`, but not the other ones proposed in the description. Maybe `total_malloc_bytes` should be renamed to `total_allocated_bytes` then, if that also count the bytes for Ruby object allocations. If that's not the case, maybe CRuby should consider exposing `total_allocated_bytes` (counting native/malloc + Ruby object allocations in bytes). BTW https://github.com/ruby/ruby/pull/3978#issuecomment-764731240 mentions
This needs to be enabled with `Thread.trace_memory_allocations=true`
I think this is good to have. The JVM has the same concept with `setThreadAllocatedMemoryEnabled`. Enabling automatically on the first call doesn't seem so nice, because it means no allocations tracked before that. Also @ioquatix mentioned in https://github.com/ruby/ruby/pull/3978#issuecomment-2705075374 it would be nice to be per Fiber instead of per Thread. On JRuby and TruffleRuby it would already be per Fiber, since each Fiber uses a java.lang.Thread (or VirtualThread < java.lang.Thread). ---------------------------------------- Feature #21042: Add and expose Thread#memory_allocations memory allocation counters https://bugs.ruby-lang.org/issues/21042#change-112321 * Author: stanhu (Stan Hu) * Status: Open * Assignee: ioquatix (Samuel Williams) ---------------------------------------- For the last 5 years, we've been patching our Ruby interpreter with https://github.com/ruby/ruby/pull/3978 in order to track memory allocations over time. This has been running in production at GitLab for a long time. I'd like to request approval for this patch to land upstream since we're getting tired of maintaining this patch, and this data seems like it would be generally useful. If this can be done via a C extension, let me know, and I can look at that. Copying from that pull request: ### Design This is designed to measure a memory allocations in a multi-threaded environments (concurrent requests processing) with an accurate information about allocated memory within a given execution context. The idea here is to provide as cheap as possible counter without an overhead of calling callbacks, and provide this information on a per-thread basis. ### Implementation This adds `Thread.current.memory_allocations`, which provides information about: * total_allocated_objects * total_malloc_bytes * total_mallocs This is based on a expectation, that allocation for a given thread always happens with a `rb_current_thread()` properly indicating a thread performing allocation. This measures total number of allocations as counters. Now, since the removal of objects is async and happening at random moment, the same cannot be said for deallocations, thus only allocations are tracked. -- https://bugs.ruby-lang.org/