PYTHON-3718 Faster INT2STRING

[thalassemia]

In _cbsonmodule.c, the INT2STRING macro is used heavily during serialization. In my workload (heavily nested documents with large array fields), this macro becomes a performance bottleneck. By swapping the macro for a more purpose-built function like this one adapted from MySQL, my insert_one calls were another 2x faster on top of the 2x speed improvement from #1219 (down to about 25% of initial runtime).

[blink1073]

Hi @thalassemia, thanks for working on this as well! I am not a lawyer, but my interpretation is that we would need to attribute the code from mysql-server, which is GPL v2.0, and considered incompatible with Apache 2.0 software.

[thalassemia]

Thanks for bringing that to my attention @blink1073! I've replaced the code that I took from mysql-server with my own, and (temporarily) included a script that tests edge cases (LLONG_MAX and LLONG_MIN) and benchmarks performance. For commonly seen integers, my code is just as performant as that of mysql-server, and both are more than 2x faster than the current macro.

[blink1073]

Thanks again! I'd feel safer if we kept a Python test to exercise the new function.

[blink1073]

Great idea!

[thalassemia]

Full credit to @1fish2! Are the Evergreen tests failing due to an issue in the PR? Can't see the details.

[blink1073]

Here's the log, note the use of setup.py build_ext -i instead of pip install -e . like we do in GitHub Actions:

 [2023/05/31 16:49:03.773] + /opt/python/3.10/bin/python3 setup.py build_ext -i
 [2023/05/31 16:49:04.056] INFO: coverage is installed, running tests with coverage...
 [2023/05/31 16:49:04.056] running clean
 [2023/05/31 16:49:04.056] running build_ext
 [2023/05/31 16:49:04.061] building 'bson._cbson' extension
 [2023/05/31 16:49:04.061] creating build
 [2023/05/31 16:49:04.061] creating build/temp.linux-x86_64-cpython-310
 [2023/05/31 16:49:04.062] creating build/temp.linux-x86_64-cpython-310/bson
 [2023/05/31 16:49:04.062] gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -Ibson -I/opt/python/3.10/include/python3.10 -c bson/_cbsonmodule.c -o build/temp.linux-x86_64-cpython-310/bson/_cbsonmodule.o
 [2023/05/31 16:49:04.920] gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -Ibson -I/opt/python/3.10/include/python3.10 -c bson/buffer.c -o build/temp.linux-x86_64-cpython-310/bson/buffer.o
 [2023/05/31 16:49:05.020] gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -Ibson -I/opt/python/3.10/include/python3.10 -c bson/time64.c -o build/temp.linux-x86_64-cpython-310/bson/time64.o
 [2023/05/31 16:49:05.228] creating build/lib.linux-x86_64-cpython-310
 [2023/05/31 16:49:05.228] creating build/lib.linux-x86_64-cpython-310/bson
 [2023/05/31 16:49:05.229] gcc -pthread -shared -Wl,--enable-new-dtags,-rpath,/opt/python/3.10/lib build/temp.linux-x86_64-cpython-310/bson/_cbsonmodule.o build/temp.linux-x86_64-cpython-310/bson/buffer.o build/temp.linux-x86_64-cpython-310/bson/time64.o -L/opt/python/3.10/lib -o build/lib.linux-x86_64-cpython-310/bson/_cbson.cpython-310-x86_64-linux-gnu.so
 [2023/05/31 16:49:05.248] building 'pymongo._cmessage' extension
 [2023/05/31 16:49:05.248] creating build/temp.linux-x86_64-cpython-310/pymongo
 [2023/05/31 16:49:05.248] gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -Ibson -I/opt/python/3.10/include/python3.10 -c bson/buffer.c -o build/temp.linux-x86_64-cpython-310/bson/buffer.o
 [2023/05/31 16:49:05.347] gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -Ibson -I/opt/python/3.10/include/python3.10 -c pymongo/_cmessagemodule.c -o build/temp.linux-x86_64-cpython-310/pymongo/_cmessagemodule.o
 [2023/05/31 16:49:05.622] creating build/lib.linux-x86_64-cpython-310/pymongo
 [2023/05/31 16:49:05.622] gcc -pthread -shared -Wl,--enable-new-dtags,-rpath,/opt/python/3.10/lib build/temp.linux-x86_64-cpython-310/bson/buffer.o build/temp.linux-x86_64-cpython-310/pymongo/_cmessagemodule.o -L/opt/python/3.10/lib -o build/lib.linux-x86_64-cpython-310/pymongo/_cmessage.cpython-310-x86_64-linux-gnu.so
 [2023/05/31 16:49:05.644] copying build/lib.linux-x86_64-cpython-310/bson/_cbson.cpython-310-x86_64-linux-gnu.so -> bson
 [2023/05/31 16:49:05.645] copying build/lib.linux-x86_64-cpython-310/pymongo/_cmessage.cpython-310-x86_64-linux-gnu.so -> pymongo
 [2023/05/31 16:49:05.693] + /opt/python/3.10/bin/python3 -c 'from bson import _cbson; from pymongo import _cmessage'
 [2023/05/31 16:49:06.038] Traceback (most recent call last):
 [2023/05/31 16:49:06.038]   File "<string>", line 1, in <module>
 [2023/05/31 16:49:06.038] ImportError: /data/mci/a4e2586048652aa5165a75ee3e206dd6/src/pymongo/_cmessage.cpython-310-x86_64-linux-gnu.so: undefined symbol: long_long_to_str
 [2023/05/31 16:49:06.068] Command 'shell.exec' in function 'run tests' failed: shell script encountered problem: exit code 1.
 [2023/05/31 16:49:06.068] Task completed - FAILURE.
 [2023/05/31 16:49:06.187] Running post-task commands.

[ShaneHarvey]

LGTM thanks!

[ShaneHarvey]

Our existing perf benchmarks don't show any improvement for this change because they don't cover encoding large arrays fields. Testing manually shows great results.

Before this change:

$ python -m timeit -s 'from bson import encode;doc={"a":list(range(1000000))}' 'encode(doc)'
5 loops, best of 5: 67.2 msec per loop

After this change:

$ python -m timeit -s 'from bson import encode;doc={"a":list(range(1000000))}' 'encode(doc)'
10 loops, best of 5: 37.7 msec per loop

That's roughly a 2x improvement. Going back further and comparing this to the commit directly before PYTHON-3717:

$ python -m timeit -s 'from bson import encode;doc={"a":list(range(1000000))}' 'encode(doc)'
1 loop, best of 5: 298 msec per loop

So this change combined with PYTHON-3717 yields up to an 8x improvement in bson encoding. Incredible! Thanks again!