Summary:
Oftentimes, users complain that a bunch of extra events are prepended to their desired GPU snapshot. This is because they usually attach an OOM logger without knowing and when they go to collect the actual snapshot, it adds all the OOM logger contents. Since OOM and regular snapshot use the same backend, we currently don't have the infra in place to split these snapshots.
As a solution we add a flag to the snapshot frontend to clear out the history when starting the auto-trace record memory history.
A more thorough solution would be to have a user pass in a handle and to have snapshots per handle to seperate the events. However, this would likely be complicated and more work than it is worth as we would have to change the callbacks in the caching allocator and pass these objects between python and cpp.
Test Plan:
See diff below
Differential Revision: D71159720
Pull Request resolved: https://github.com/pytorch/pytorch/pull/149352
Approved by: https://github.com/eqy, https://github.com/aaronenyeshi
Summary: Should skip C++ warmup `unwind::unwind();` if there is no context set. This call is sometimes causing hanging issues since C++ stack collection is not robust.
Test Plan: CI
Differential Revision: D60965985
Pulled By: aaronenyeshi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/133038
Approved by: https://github.com/eqy
Summary: Instead of embedding the user_defined TraceEntry inside of device_traces, which causes issues when some threads may not have the proper device id set, save them into an external_annotations field by using a RingBuffer<AnnotationEntry> called annotation_buffer owned by the NativeCachingAllocator.
Test Plan: CI, resnet run, and FBR model.
Differential Revision: D59703213
Pulled By: aaronenyeshi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/130964
Approved by: https://github.com/zdevito
Summary: Make the recordAnnotations' Record function callback lazily initialize when record memory history starts. This will help reduce the impact on Time To First Batch metric.
Test Plan: CI and ran locally.
Differential Revision: D58875576
Pulled By: aaronenyeshi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/129242
Approved by: https://github.com/zdevito
Summary:
Add new traceEvents into Memory Snapshot for record_function annotations. These will capture both the profiler's step annotation as well as user annotations.
Test Plan:
CI
Pulled By:
aaronenyeshi
Differential Revision: D55941362
Pull Request resolved: https://github.com/pytorch/pytorch/pull/129072
Approved by: https://github.com/zdevito
Previously when we recorded a free action in a memory trace, we would provide
the stack for when the block was allocated. This is faster because we do not
have to record stacks for free, which would otherwise double the number of stacks
collected. However, sometimes knowing the location of a free is useful for
figuring out why a tensor was live. So this PR adds this behavior. If
performance ends up being a concern the old behavior is possible by passing
"alloc" to the context argument rather than "all".
Also refactors some of glue logic to be consistent across C++ and Python and
routes the Python API through the C++ version.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106758
Approved by: https://github.com/albanD
We want to display the stack for the original cudaMalloc that created a segment.
Previously we could only report the last time the segment memory was used,
or the record of the segment_alloc could appear in the list of allocator actions.
This PR ensure regardless of whether we still have the segment_alloc action,
the context for a segment is still available. The visualizer is updated to
be able to incorporate this information.
This PR adds a new field to Block. However the previous stacked cleanup PR
removed a field of the same size, making the change to Block size-neutral.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106113
Approved by: https://github.com/aaronenyeshi
For free blocks of memory in the allocator, we previously kept a linked list
of the stack frames of previous allocations that lived there. This was only
ever used in one flamegraph visualization and never proved useful at
understanding what was going on. When memory history tracing was added, it
became redundant, since we can see the history of the free space from recording
the previous actions anyway.
This patch removes this functionality and simplifies the snapshot format:
allocated blocks directly have a 'frames' attribute rather than burying stack frames in the history.
Previously the memory history tracked the real size of allocations before rounding.
Since history was added, 'requested_size' has been added directly to the block which records the same information,
so this patch also removes that redundancy.
None of this functionality has been part of a PyTorch release with BC guarentees, so it should be safe to alter
this part of the format.
This patch also updates our visualization tools to work with the simplified format. Visualization tools keep
support for the old format in `_legacy` functions so that during the transition old snapshot files can still be read.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106079
Approved by: https://github.com/eellison
Common advice we give for handling memory fragmentation issues is to
allocate a big block upfront to reserve memory which will get split up later.
For programs with changing tensor sizes this can be especially helpful to
avoid OOMs that happen the first time we see a new largest input and would
otherwise have to allocate new segments.
However the issue with allocating a block upfront is that is nearly impossible
to correctly estimate the size of that block. If too small, space in the block
will run out and the allocator will allocate separate blocks anyway. Too large,
and other non-PyTorch libraries might stop working because they cannot allocate
any memory.
This patch provides the same benefits as using a pre-allocating block but
without having to choose its size upfront. Using the cuMemMap-style APIs,
it adds the ability to expand the last block in a segment when more memory is
needed.
Compared to universally using cudaMallocAsync to avoid fragmentation,
this patch can fix this common fragmentation issue while preserving most
of the existing allocator behavior. This behavior can be enabled and disabled dynamically.
This should allow users to, for instance, allocate long-lived parameters and state in individual buffers,
and put temporary state into the large expandable blocks, further reducing
fragmentation.
See inline comments for information about the implementation and its limitations.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96995
Approved by: https://github.com/eellison
This refactors the stack trace facility specific to memory profiling
in python+cuda to make a generic facility to generate combined stack
traces.
The generic facility (combined_traceback.h) does not require
python to be around to work, but will return python stacks if it is
present.
This facility is then used to add support for stack trace gathering in memory profiling that
happens directly from C++.
It is also used to expose a python API for gathering and symbolizing
combineds stacks.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95541
Approved by: https://github.com/ezyang
Copying note from cuda caching allocator:
```
* Note [Checkpointing PrivatePoolState]
*
* Refer above to Note [Interaction with CUDA graph capture]. Allocations made
* during graph capture are made from a separate private pool. During graph
* capture allocations behave as usual. During graph replay the allocator
* state does not change even as new tensors are created. The private pool
* will not free its blocks to the main caching allocator until cuda graph use
* is finished to prevent an allocation from eager clobbering the memory from
* a live but unaccounted for tensor that was created during replay.
*
* `make_graphed_callables`, a series of separate callables chained in
* successive cuda graphs, can share a memory pool because after a cuda graph
* recording the allocations in the shared private pool exactly reflect the
* tensors that are allocated.
*
* We would like to extend callable chaining to support a graphed callable
* tree. In this scenario, we have a tree of callable chains which will be
* captured with cuda graphs. In the diagram below, we have a tree with four
* callables, A, B, C, and D. Suppose we have captured, and subsequently
* replayed, A, B, and C. Then on a new invocation, we replay A and B, but
* would now like to record D. At this point the private pool will not reflect
* any of the live tensors created during graph replay. Allocations made
* during a new recording with the pool could overwrite those live tensors.
*
* In order to record a new graph capture after replaying prior callables in
* the tree, we need the allocator to reflect the state of the live tensors.
* We checkpoint the state of the private after each recording, and then
* reapply it when we are starting a new recording chain. Additionally, we
* must free the allocations for any tensors that died between the end of our
* previous graph replaying and our new recording (TODO). All of the allocated
* segments that existed in the checkpointed state must still exist in the
* pool. There may also exist new segments, which we will free (TODO : link
* note [live tensors between iterations] when it exists).
*
*
* ---------------> A ---------------> B ---------------> C
* |
* |
* |
* |
* ---------------> D
```
A few TODOs:
- need to add logic for freeing tensors that have died between a last replay and current new recording
- Add logic for free that might be called on a pointer multiple times (because we are manually freeing live tensors)
The two scenarios above have not been exercised in the tests yet.
Differential Revision: [D43999889](https://our.internmc.facebook.com/intern/diff/D43999889)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94653
Approved by: https://github.com/zdevito
Summary:
The caching allocator can be configured to round memory allocations in order to reduce fragmentation. Sometimes however, the overhead from rounding can be higher than the fragmentation it helps reduce.
We have added a new stat to CUDA caching allocator stats to help track if rounding is adding too much overhead and help tune the roundup_power2_divisions flag:
- "requested_bytes.{current,peak,allocated,freed}": memory requested by client code, compare this with allocated_bytes to check if allocation rounding adds too much overhead
Test Plan: Added test case in caffe2/test/test_cuda.py
Differential Revision: D40810674
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88575
Approved by: https://github.com/zdevito
We currently can take snapshots of the state of the allocated cuda memory, but we do not have a way to correlate these snapshots with the actions the allocator that were taken between snapshots. This PR adds a simple fixed-sized buffer that records the major actions that the allocator takes (ALLOC, FREE, SEGMENT_ALLOC, SEGMENT_FREE, OOM, SNAPSHOT) and includes these with the snapshot information. Capturing period snapshots with a big enough trace buffer makes it possible to see how the allocator state changes over time.
We plan to use this functionality to guide how settings in the allocator can be adjusted and eventually have a more robust overall algorithm.
As a component of this functionality, we also add the ability to get a callback when the allocator will throw an OOM, primarily so that snapshots can be taken immediately to see why the program ran out of memory (most programs have some C++ state that would free tensors before the OutOfMemory exception can be caught).
This PR also updates the _memory_viz.py script to pretty-print the trace information and provide a better textual summary of snapshots distinguishing between internal and external fragmentation.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86241
Approved by: https://github.com/ngimel
Sometimes the driving process want to save memory snapshots but isn't Python.
Add a simple API to turn it on without python stack traces. It still
saves to the same format for the vizualization and summary scripts, using
the C++ Pickler.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86190
Approved by: https://github.com/ezyang
