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[enhancement] limit cmake jobs for Windows backend build #2240

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[enhancement] limit cmake jobs for Windows backend build #2240

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63a92f8
Update build_backend.py
icfaust Jan 3, 2025
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Update build_backend.py
icfaust Jan 3, 2025
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icfaust Jan 3, 2025
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fix memfree
icfaust Jan 3, 2025
ee7cbf9
Update build_backend.py
icfaust Jan 3, 2025
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Update build_backend.py
icfaust Jan 4, 2025
73d787b
Update build_backend.py
icfaust Jan 7, 2025
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26 changes: 22 additions & 4 deletions scripts/build_backend.py
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Original file line number Diff line number Diff line change
Expand Up @@ -131,16 +131,34 @@
cmake_args += ["-DADD_ONEDAL_RPATH=ON"]

cpu_count = multiprocessing.cpu_count()
# convert to max supported pointer to a memory size in kB
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I'm not getting the idea here. sys.maxsize returns you the maximum possible addressable memory range by the operating system in bytes, which in a modern machine would be 2^63 (expressing it in KiB would require division by 2^10).

Dividing that by 128 would not have any effect, since the available memory might be in the range of 2^33 through 2^38 or so for a modern machine.

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Changed, was confused a little about Py_ssize_t definition and how it relates to size_t. I have switched division operators to bitshifts for clarity and directness.

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Given the exact numbers that you are arriving at, is this trying to limit addressable space to accommodate a float64 casted to size_t? What's the idea behind these?

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Yeah, I am assuming that the underlying processes have a memory bound (not just linux or windows). I wanted a general value I could easily get out of python to have a conservative upper bound of memory that can be used. I then use that as a very large initial value for splitting it in the multiprocessing. I am using Py_ssize_t like sizeof to yield the largest byte value possible for a platform. This at least makes all platforms to have some sort of bound without having to explicitly handle other platforms beyond windows/linux (e.g. mac).

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Am I understanding it correctly that the purpose of this code is to spawn multiple compilation processes with a memory limit for each such that the sum would not exceed system memory? Or does this code serve some other purpose?

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Maybe a reasonable compromise would be to just get total RAM in the system and divide by 4GB to get a target number of max parallel processes. I don't think the problem is approachable otherwise - new processes can be spawned and terminated by the user as the compilation is running either way, which also changes the calculation.

It's also quite an odd thing to have in a project's build script. I am not aware of any other ML library limiting the number of parallel jobs for the user based on available RAM - typically they just OOM on their own and the user then needs to adjust threads as needed.

Was there a CI failure on windows due to OOM?

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No error that I saw for windows, I assume it was out of memory on Linux at some point? @Alexsandruss

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@Alexsandruss Alexsandruss Jan 7, 2025 •
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1GB constraint was chosen in #1196 based on CI VM parameters to prevent build failure due to OOM on Linux only. Change to some other working weak constraint will be fine. Also, MemFree might be changed to MemAvailable.

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@icfaust icfaust Jan 8, 2025 •
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@david-cortes-intel Maybe we should allow for external control of the parallel processes (something like MAX_JOBS from pytorch https://github.com/pytorch/pytorch/blob/main/setup.py#L13)? The explanation shows it was done to match CI rather than a consistent error for building. That way it can be hardware agnostic and we can easily add it externally to the CI yamls without massively changing any of the build scripts. Let me know what you think. If so, then I think we would need to close this PR and make a ticket. @Alexsandruss was there a ticket generated for this TODO?

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Yes, I think a user-configurable variable would be the best solution here.

memfree = sys.maxsize // (128 if sys.maxsize > 2**32 else 256)
# limit parallel cmake jobs if memory size is insufficient
# TODO: add on all platforms
if IS_LIN:
with open("/proc/meminfo", "r") as meminfo_file_obj:
memfree = meminfo_file_obj.read().split("\n")[1].split(" ")
while "" in memfree:
memfree.remove("")
memfree = int(memfree[1]) # total memory in kB
cpu_count = min(cpu_count, floor(max(1, memfree / 2**20)))

memfree = int(memfree[1]) # total free physical memory in kB
elif IS_WIN:
txt = subprocess.run(
[
"powershell",
"Get-CIMInstance",
"Win32_OperatingSystem",
"|",
"Select",
"FreePhysicalMemory",
],
stdout=subprocess.PIPE,
text=True,
)

Check notice on line 155 in scripts/build_backend.py

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codefactor.io / CodeFactor

scripts/build_backend.py#L144-L155 

Starting a process with a partial executable path (B607)
memfree = int(
txt.stdout.strip().split(" ")[-1]
) # total free physical memory in kB

mem_per_proc = 2**20 # approximately 1GB
cpu_count = min(cpu_count, floor(max(1, memfree / mem_per_proc)))
make_args = ["cmake", "--build", abs_build_temp_path, "-j " + str(cpu_count)]

make_install_args = [
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