gh-122931 Allow stable API extensions to include a multiarch tuple in the filename #122917
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…ple in the filename This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can. It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.
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…ple in the filename This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can. It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.
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You should document this change in https://docs.python.org/dev/whatsnew/3.14.html (Doc/whatsnew/3.14.rst). I expect that you would elaborate a bit on the usage, how to use the feature, why it's needed, etc.
Done. FWIW, in Debian we plan to backport this to 3.13 too. |
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I'm only aware of Debian who uses "multiarch". Do other operating systems also use it? Maybe Debian variants, Ubuntu, and Ubuntu variants? This change will slow down any "import module". I don't recall if there is a cache for that or not. |
All Debian derivatives, yes. They typically don't deviate very much, when it comes to plumbing. |
What do you want to do about that? Is there a benchmark you'd like to see results for? I see a table of 5 entries (including NULL) increasing to 6. That is one extra item to search, when:
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Example of command: strace output: Internally, when Python imports the If we add a new entry to the import suffix, it will add one fstat() syscall per import (at least, to import a package). We should consider the impact on performance if we decide to add this feature. |
FWIW: macOS, iOS and Android all use However, on iOS and Android, there's limited need to keep binary artefacts in the same folder, as any given executable can only have a single architecture's executables. In addition, in the case of iOS, the binaries need to be migrated to the Frameworks folder and named as Frameworks, so any "side-by-side" benefits would be lost. Any "other platform" executables need to be stripped out as part of the build process, at which point there's no naming conflict. macOS uses the multiarch config value, but the value is always "darwin", and the universal binary format exists to support multiple architectures in a single binary file. I guess it might be useful to be able to have x86_64 and ARM64 binaries side-by-side... but there's probably only a year or two left in the official supported life of x86_64, so I don't think adding this feature will ultimately be that helpful for the macOS use case. |
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@stefanor: Did you consider to maintain this change as a downstream-only patch in Debian? If you would like to make it upstream, I would suggest making it optional, disabled by default, and add a configure option to enable it. That's how I added some Fedora specific changes, such as: |
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Here are some benchmarks: There is no discernable performance difference in minimal interpreter startup import time
import sys
from subprocess import check_call
t1 = time.perf_counter()
for i in range(1000):
check_call([sys.executable, "-c", ""])
t2 = time.perf_counter()
print((t2-t1) / 1000)
Looking at strace, I see only a single extra syscall. We can manufacture an import-intensive benchmark: import pkgutil
import time
t1 = time.perf_counter()
for module in pkgutil.walk_packages(onerror=lambda pkg: None):
if module.name.startswith("test."):
continue
if module.name.endswith(".__main__"):
continue
if module.name in {"antigravity", "idlelib.idle", "this", "zen"}:
continue
try:
__import__(module)
except Exception:
pass
t2 = time.perf_counter()
print((t2 - t1))
Analysing this, I see 116 stat syscalls on |
Also, note that this is used on all linux platforms. The default for (non-stable ABI) extensions is to include the multiarch tuple in the extension filename. Pick a random binary wheel built in manylinux, and you'll see them.
I would be happy to do that. Although I prefer not carrying downstream-only patches long-term if possible. Look at the mess around Without this MR, there's no real point in supporting the multiarch tags in the non-stable ABI extensions. Either we get the benefit from doing it everywhere, or you say you don't need to support the feature, and we rip it out everywhere. We've got half a feature at the moment. Would you prefer it to all be behind a config argument?
These are not entirely Fedora-specific. And that's a good argument for always trying to upstream.
In Debian we use those paths for our cross-compilers. I imagine there is a scenario where it's useful to have Python headers in there.
We're a happy customer of this too, It meant one less patch to carry. |
Maybe 0.5% slowdown with PGO. For 1 extra syscall, I'm surprised it's visible. This may still not be significant.
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@erlend-aasland @encukou: Would you mind to have a look at this issue? What do you think? Should it become the default behavior, or should it be a configure option? |
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IMO, the most important thing here is to keep this in mind for |
Yeah, that sounds sensible.
Is that expected? We've been on abi3 for quite a while. |
If we want that for the stable ABI, do we want to do the same thing for the regular ABI? It would probably affect a lot of build systems that assume they can name their output |
Yes, over a decade. abi3 showing its age, and since it's incompatible free-threading we'll need a new alternative soon.
I don't see much reason to deprecate and remove that, so that we don't break the build systems you mention. (Note that even abi3/abi4 extensions will work with a bare |
I'm going to include it in our 3.13.0 upload. |
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🔔 (I'd like to remind people to please consider this) |
…ple in the filename This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can. It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.
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…ple in the filename This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can. It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.
e649375 to
942c114
Compare
…ple in the filename This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can. It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.
942c114 to
65e8306
Compare
This permits stable ABI extensions for multiple architectures to be co-installed into the same directory, without clashing with each other, the same way (non-stable ABI) regular extensions can.
It is listed below the current .abi3 suffix because setuptools will select the first suffix containing .abi3, as the target filename. We do this to protect older Python versions predating this patch.