# Context
Previously, we would modify the parent process's NUMA bindings in order to force child process to inherit them.
However, this would not work correctly if `start_method="forkserver"`, because the subprocesses would actually inherit their bindings from the forkserver middleman process. In this case, the inherited affinity would actually be incorrect for all but the first subprocess (because the forkserver process would get created lazily, and hence inherit and then stick with the bindings intended for the first subprocess).
# This PR
* `str` entrypoints: Use `numactl` CLI
* `Callable` entrypoints: Wrap the `Callable` entrypoint and call `os.sched_setaffinity` inside it.
Hopefully this will be the last necessary iteration.
# Test Plan
## Automated
`$ pytest test/test_numa_binding.py`
## Manual
Verified flops/sec and memory locality wins on several different types of jobs
* `Callable` with forkserver
* `str` entrypoint with spawn
* `Callable` entrypoint with spawn
More details in [this doc (Meta-only).](https://docs.google.com/document/d/1vxD-OKYBTT27jbBwtW9iz9g0tNM0u-i0tiTJg_ieQA8/edit?tab=t.scjv58yswi64)
# Later PR
Update all the documentation when we're confident this has stabilized.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/166026
Approved by: https://github.com/d4l3k
Co-authored-by: PyTorch MergeBot <pytorchmergebot@users.noreply.github.com>
This PR enables all PIE rules on ruff, there are already some enabled rules from this family, the new added rules are
```
PIE796 Enum contains duplicate value: {value}
PIE808 Unnecessary start argument in range
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/165814
Approved by: https://github.com/ezyang
This PR enables all PIE rules on ruff, there are already some enabled rules from this family, the new added rules are
```
PIE796 Enum contains duplicate value: {value}
PIE808 Unnecessary start argument in range
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/165814
Approved by: https://github.com/ezyang
This PR is greatly simplified now that it stacked on top of a PR that builds with distributed always. We only need to stub functions that may not be defined due to a backend not being enabled.
Signed-off-by: Edward Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/159889
Approved by: https://github.com/wconstab
ghstack dependencies: #160449
This PR is greatly simplified now that it stacked on top of a PR that builds with distributed always. We only need to stub functions that may not be defined due to a backend not being enabled.
Signed-off-by: Edward Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/159889
Approved by: https://github.com/wconstab
ghstack dependencies: #160449
This PR is greatly simplified now that it stacked on top of a PR that builds with distributed always. We only need to stub functions that may not be defined due to a backend not being enabled.
Signed-off-by: Edward Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/159889
Approved by: https://github.com/wconstab
ghstack dependencies: #160449
This PR is greatly simplified now that it stacked on top of a PR that builds with distributed always. We only need to stub functions that may not be defined due to a backend not being enabled.
Signed-off-by: Edward Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/159889
Approved by: https://github.com/wconstab
ghstack dependencies: #160449
This PR is greatly simplified now that it stacked on top of a PR that builds with distributed always. We only need to stub functions that may not be defined due to a backend not being enabled.
Signed-off-by: Edward Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/159889
Approved by: https://github.com/wconstab
ghstack dependencies: #160449
# Context
In #161183, we added NUMA-binding support for `Callable` entrypoints to `elastic_launch`.
However, we would raise an exception if the subprocesses would be spawned in parallel via `ThreadPoolExecutor`, which is an option configurable via the `TORCH_MP_PARALLEL_START` environment variable (see diff).
The logic here was that `os.sched_setaffinity`, which we used to set CPU affinities, is [per process](https://docs.python.org/3/library/os.html#os.sched_setaffinity), so there could be a race condition during a parallel start:
> Restrict the process with PID pid (or the current process if zero) to a set of CPUs. mask is an iterable of integers representing the set of CPUs to which the process should be restricted.
But on further reading, the Linux docs say [`sched_setaffinity` is per *thread*.](https://man7.org/linux/man-pages/man2/sched_setaffinity.2.html) As it turns out, the Python doc is a misnomer.
I [verified that `sched_setaffinity` only affects the calling thread, not the entire calling process.](https://gist.github.com/pdesupinski/7e2de3cbe5bb48d489f257b83ccddf07)
The upshot is that we actually *can* safely use the inheritance trick from #161183 even with parallel start, since the setting will be inherited from the calling thread, and `os.sched_setaffinity` only affects the calling thread.
# This PR
Remove restrictions against parallel start for NUMA binding.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/161576
Approved by: https://github.com/d4l3k
# Context
In #160163, we added support for NUMA binding for `Callable` entrypoints to `elastic_launch`. This requires special consideration, because they go through a different path to spawn subprocesses compared to `str` entrypoints, a path which does not provide a straightforward way to utilize `numactl` CLI. See #160006 for a full description of the challenges.
Although #160163 worked in initial local experiments, we ran into some linker errors in other environments when we tried to call `numactl`. This appeared to be due to interactions with how the `LD_PRELOAD` environment variable was being set.
# This PR
On further thought, the most straightforward, foolproof solution here is to use [the trick that @d4l3k suggested.](https://github.com/pytorch/pytorch/issues/160006#issuecomment-3162018836)
Specifically, for each local rank `i`:
1. The parent process sets its own CPU affinity to what local rank `i`'s should be.
2. Then, the parent spawns the subprocess for local rank `i`.
3. Finally, the parent resets its own CPU affinity to what it was originally.
There were other solutions that would work just for `Callable` entrypoints, but I believe this is the simplest one that can work for *both* `str` and `Callable`, and it's pretty simple.
This required a bit of refactoring:
1. Turn all the `_get_.*_numactl_options` into functions which return a set of logical CPUs to bind to, rather than options like `--cpunodebind=0`.
2. Instead of wrapping commands with `numactl`, use `os.sched_setaffinity` to bind to the CPUs from (1.).
3. Put this all inside a context manager which encapsulates applying and restoring the bindings in the parent process.
4. Use the context manager for both `str` and `Callable` paths
# Test Plan
## Automated
`$ pytest test/test_numa_binding.py`
## Manual
See [doc.](https://docs.google.com/document/d/1vxD-OKYBTT27jbBwtW9iz9g0tNM0u-i0tiTJg_ieQA8/edit?tab=t.0) Meta only, but TLDR tried out every combination of `str`, `Callable`, binding disabled, and binding enabled on the same model and saw 2x SM utilization for binding enabled.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/161183
Approved by: https://github.com/d4l3k
# Context
Another fix to enable broad rollout of #149334.
The implementation assumes that the trainer process with local rank `n` only uses device `cuda:n`. However, there are sometimes jobs with more than one GPU per process, in which case our assumption could be incorrect and actually lead to worse memory locality.
# This PR
As titled.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/160848
Approved by: https://github.com/kiukchung
# Context
Broader context in #160163.
In order for the _utils_internal version of signpost_event to do proper logging, its parameters argument needs to be json serializable.
# This PR
Convert `NumaOptions` to serializable form before inputting to `signpost_event`.
# Test Plan
## Automated
Added tests `$ pytest test/test_numa_binding.py`.
## Manual
See [D80317206](https://www.internalfb.com/diff/D80317206).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/160710
Approved by: https://github.com/kiukchung
# Context
This is an extension of #149334.
# This PR
Add support for NUMA bindings with Callable entrypoints, such as `do_train` instead of `/usr/local/bin/python`.
Most notably, we utilize a hack in order to force `Process.start()` to use custom NUMA bindings for each subprocess. Please search for `HACK:` in the code to see a description of the implementation we chose, and #160006 for discussion of alternatives and why this is necessary.
Other changes:
* Remove unnecessary `--preferred` option from all binding strategies. By default, Linux already allocates memory to the NUMA node local to the CPU which triggered the allocation. (See [MPOL_LOCAL](https://man7.org/linux/man-pages/man2/set_mempolicy.2.html).)
* Refactor so that the main API is `maybe_wrap_command_with_numa_bindings`, which computes bindings for a single rank at a time, rather than `maybe_wrap_with_numa_bindings` which computed bindings for all ranks at once. This allowed for more code sharing between `Callable` and `str` entrypoints.
# Test Plan
## Automated
`$ pytest test/test_numa_binding.py`
## Manual
Using [this benchmark,](https://gist.github.com/pdesupinski/bbe01ade455d86e989794f2c612e2d91), ran
```
$ PYTHONUNBUFFERED=1 LOGLEVEL=INFO perf stat -e ls_dmnd_fills_from_sys.dram_io_far,ls_dmnd_fills_from_sys.dram_io_near -- python -m torch.distributed.run --standalone --nproc-per-node=8 --numa-binding=node --run-path mlp_train.py 2>&1 | tee node_callable.txt && PYTHONUNBUFFERED=1 LOGLEVEL=INFO perf stat -e ls_dmnd_fills_from_sys.dram_io_far,ls_dmnd_fills_from_sys.dram_io_near -- python -u -m torch.distributed.run --standalone --nproc-per-node=8 --run-path mlp_train.py 2>&1 | tee none_callable.txt
```
and observed
* 6.6% remote memory accesses with 'node' bindings
* 11.6% remote without bindings
I also ran similar with `str` entrypoints as before just to be sure it's still working.
NOTE: [--run-path triggers the code to be run inside a `Callable`.](017259f9c6/torch/distributed/run.py (L870))
Pull Request resolved: https://github.com/pytorch/pytorch/pull/160163
Approved by: https://github.com/d4l3k
