PyPy (Posts about casestudy)

Guest Post: How PortaOne uses PyPy for high-performance processing, connecting over 1B of phone calls every month

The PyPy Team — Thu, 29 Aug 2024 09:00:00 GMT

The PyPy project is always happy to hear about industrial use and deployments of PyPy. For the GC bug finding task earlier this year, we collaborated with PortaOne and we're super happy that Serhii Titov, head of the QA department at PortaOne, was up to writing this guest post to describe their use and experience with the project.

What does PortaOne do?

We at PortaOne Inc. allow telecom operators to launch new services (or provide existing services more efficiently) using our VoIP platform (PortaSIP) and our real-time charging system (PortaBilling), which provides additional features for cloud PBX, such as call transfer, queues, interactive voice response (IVR) and more. At this moment our support team manages several thousand servers with our software installed in 100 countries, through which over 500 telecommunication service providers connect millions of end users every day. The unique thing about PortaOne is that we supply the source code of our product to our customers - something unheard of in the telecom world! Thus we attract "telco innovators", who use our APIs to build around the system and the source code to create unique tweaks of functionality, which produces amazing products.

At the core of PortaSIP is the middle-ware component (the proper name for it is "B2BUA", but that probably does not say much to anyone outside of experts in VoIP), which implements the actual handling of SIP calls, messages, etc. and all added features (for instance, trying to send a call via telco operators through which the cost per minute is lower). It has to be fast (since even a small delay in establishing a call is noticed by a customer), reliable (everyone hates when a call drops or cannot be completed) and yet easily expandable with new functionality. This is why we decided to use Python as opposed to C/C++ or similar programming languages, which are often used in telecom equipment.

The B2BUA component is a batch of similar Python processes that are looped inside a asyncore.dispatcher wrapper. The load balancing between these Python processes is done by our stateless SIP proxy server written in C++. All our sockets are served by this B2BUA. We have our custom client-wrappers around pymysql, redis, cassandra-driver and requests to communicate with external services. Some of the Python processes use cffi wrappers around C-code to improve their performance (examples: an Oracle DB driver, a client to a radius server, a custom C logger).

The I/O operations that block the main thread of the Python processes are processed in sub-threads. We have custom wrappers around threading.Thread and also asyncore.dispatcher. The results of such operations are returned to the main thread.

Improving our performance with PyPy

We started with CPython and then in 2014 switched to PyPy because it was faster. Here's an exact quote from our first testing notes: "PyPy gives significant performance boost, ~50%". Nowadays, after years of changes in all the software involved, PyPy still gives us +50% boost compared to CPython.

Taking care of real time traffic for so many people around the globe is something we're really proud of. I hope the PyPy team can be proud of it as well, as the PyPy product is a part of this solution.

Finding a garbage collector bug: stage 1, the GC hooks

However our path with PyPy wasn't perfectly smooth. There were very rare cases of crashes on PyPy that we weren't able to catch. That's because to make coredump useful we needed to switch to PyPy with debug, but we cannot let it run in that mode on a production system for an extended period of time, and we did not have any STR (steps-to-reproduce) to make PyPy crash again in our lab. That's why we kept (and still keep) both interpreters installed just in case, and we would switch to CPython if we noticed it happening.

At the time of updating PyPy from 3.5 to 3.6 our QA started noticing those crashes more often, but we still had no luck with STR or collecting proper coredumps with debug symbols. Then it became even worse after our development played with the Garbage Collector's options to increase performance of our middleware component. The crashes started to affect our regular performance testing (controlled by QA manager Yevhenii Bovda). At that point it was decided that we can no longer live like that and so we started an intense investigation.

During the first stage of our investigation (following the best practice of troubleshooting) we narrowed down the issue as much as we could. So, it was not our code, it was definitely somewhere in PyPy. Eventually our SIP software engineer Yevhenii Yatchenko found out that this bug is connected with the use of our custom hooks in the GC. Yevhenii created ticket #4899 and within 2-3 days we got a fix from a member of the PyPy team, in true open-source fashion.

Finding a garbage collector bug: stage 2, the real bug

Then came stage 2. In parallel with the previous ticket, Yevhenii created #4900 that we still see failing with coredumps quite often, and they are not connected to GC custom hooks. In a nutshell, it took us dozens of back and forward emails, three Zoom sessions and four versions of a patch to solve the issue. During the last iteration we got a new set of options to try and a new version of the patch. Surprisingly, that helped! What a relief! So, the next logical step was to remove all debug options and run PyPy only with the patch. Unfortunately, it started to fail again and we came to the obvious conclusion that what will help us is not a patch, but one of options we were testing out. At that point we found out that PYPY_GC_MAX_PINNED=0 is a necessary and sufficient condition to solve our issue. This points to another bug in the garbage collector, somehow related to object pinning.

Here's our current state: we have to add PYPY_GC_MAX_PINNED=0, but we do not face the crashes anymore.

Conclusion and next steps

Gratitude is extended to Carl for his invaluable assistance in resolving the nasty bugss, because it seems we're the only ones who suffered from the last one and we really did not want to fall back to CPython due to its performance disadvantage.

Serhii Titov, head of the QA department at PortaOne Inc.

P.S. If you are a perfectionist and at this point you have mixed feelings and you are still bothered by the question "But there might still be a bug in the GC, what about that?" - Carl has some ideas about it and he will sort it out (we will help with the testing/verification part).

RPython-based emulator speeds up RISC-V simulation over 15x

CF Bolz-Tereick — Tue, 16 May 2023 11:22:35 GMT

In cooperation with RISC-V International, who funded a part of this project, we recently created a workflow to use RPython to take a Sail RISC-V model and automatically create a RISC-V ISA emulator from it, which we call Pydrofoil. The simulator sped up booting a linux emulator from 35 minutes (using the standard Sail-generated emulator in C) to 2 minutes, a speedup of 17.5x. More details about the process are in the RISC-V blog post.

A few take-aways from the project:

While PyPy has shown it can speed up generic python code about 4x, the technology behind PyPy can really shine in other areas.
RPython is malleable and can be molded to many tasks, the RPython meta-JIT is very flexible.
A JIT is well-suited for the problem of emulation, because it can perform dynamic binary translation.

PyPy can solve real world performance problems, even somewhat unusual ones. Please get in touch and let us know how we can help you solve yours!

Natural Language Processing for Icelandic with PyPy: A Case Study

Vilhjálmur Þorsteinsson — Sun, 06 Feb 2022 15:00:00 GMT

Natural Language Processing for Icelandic with PyPy: A Case Study

Icelandic is one of the smallest languages of the world, with about 370.000 speakers. It is a language in the Germanic family, most similar to Norwegian, Danish and Swedish, but closer to the original Old Norse spoken throughout Scandinavia until about the 14th century CE.

As with other small languages, there are worries that the language may not survive in a digital world, where all kinds of fancy applications are developed first - and perhaps only - for the major languages. Voice assistants, chatbots, spelling and grammar checking utilities, machine translation, etc., are increasingly becoming staples of our personal and professional lives, but if they don’t exist for Icelandic, Icelanders will gravitate towards English or other languages where such tools are readily available.

Iceland is a technology-savvy country, with world-leading adoption rates of the Internet, PCs and smart devices, and a thriving software industry. So the government figured that it would be worthwhile to fund a 5-year plan to build natural language processing (NLP) resources and other infrastructure for the Icelandic language. The project focuses on collecting data and developing open source software for a range of core applications, such as tokenization, vocabulary lookup, n-gram statistics, part-of-speech tagging, named entity recognition, spelling and grammar checking, neural language models and speech processing.

My name is Vilhjálmur Þorsteinsson, and I’m the founder and CEO of a software startup Miðeind in Reykjavík, Iceland, that employs 10 software engineers and linguists and focuses on NLP and AI for the Icelandic language. The company participates in the government’s language technology program, and has contributed significantly to the program’s core tools (e.g., a tokenizer and a parser), spelling and grammar checking modules, and a neural machine translation stack.

When it came to a choice of programming languages and development tools for the government program, the requirements were for a major, well supported, vendor-and-OS-agnostic FOSS platform with a large and diverse community, including in the NLP space. The decision to select Python as a foundational language for the project was a relatively easy one. That said, there was a bit of trepidation around the well known fact that CPython can be slow for inner-core tasks, such as tokenization and parsing, that can see heavy workloads in production.

I first became aware of PyPy in early 2016 when I was developing a crossword game Netskrafl in Python 2.7 for Google App Engine. I had a utility program that compressed a dictionary into a Directed Acyclic Word Graph and was taking 160 seconds to run on CPython 2.7, so I tried PyPy and to my amazement saw a 4x speedup (down to 38 seconds), with literally no effort besides downloading the PyPy runtime.

This led me to select PyPy as the default Python interpreter for my company’s Python development efforts as well as for our production websites and API servers, a role in which it remains to this day. We have followed PyPy’s upgrades along the way, being just about to migrate our minimally required language version from 3.6 to 3.7.

In NLP, speed and memory requirements can be quite important for software usability. On the other hand, NLP logic and algorithms are often complex and challenging to program, so programmer productivity and code clarity are also critical success factors. A pragmatic approach balances these factors, avoids premature optimization and seeks a careful compromise between maximal run-time efficiency and minimal programming and maintenance effort.

Turning to our use cases, our Icelandic text tokenizer "Tokenizer" is fairly light, runs tight loops and performs a large number of small, repetitive operations. It runs very well on PyPy’s JIT and has not required further optimization.

Our Icelandic parser Greynir (known on PyPI as reynir) is, if I may say so myself, a piece of work. It parses natural language text according to a hand-written context-free grammar, using an Earley-type algorithm as enhanced by Scott and Johnstone. The CFG contains almost 7,000 nonterminals and 6,000 terminals, and the parser handles ambiguity as well as left, right and middle recursion. It returns a packed parse forest for each input sentence, which is then pruned by a scoring heuristic down to a single best result tree.

This parser was originally coded in pure Python and turned out to be unusably slow when run on CPython - but usable on PyPy, where it was 3-4x faster. However, when we started applying it to heavier production workloads, it became apparent that it needed to be faster still. We then proceeded to convert the innermost Earley parsing loop from Python to tight C++ and to call it from PyPy via CFFI, with callbacks for token-terminal matching functions (“business logic”) that remained on the Python side. This made the parser much faster (on the order of 100x faster than the original on CPython) and quick enough for our production use cases. Even after moving much of the heavy processing to C++ and using CFFI, PyPy still gives a significant speed boost over CPython.

Connecting C++ code with PyPy proved to be quite painless using CFFI, although we had to figure out a few magic incantations in our build module to make it compile smoothly during setup from source on Windows and MacOS in addition to Linux. Of course, we build binary PyPy and CPython wheels for the most common targets so most users don’t have to worry about setup requirements.

With the positive experience from the parser project, we proceeded to take a similar approach for two other core NLP packages: our compressed vocabulary package BinPackage (known on PyPI as islenska) and our trigrams database package Icegrams. These packages both take large text input (3.1 million word forms with inflection data in the vocabulary case; 100 million tokens in the trigrams case) and compress it into packed binary structures. These structures are then memory-mapped at run-time using mmap and queried via Python functions with a lookup time in the microseconds range. The low-level data structure navigation is done in C++, called from Python via CFFI. The ex-ante preparation, packing, bit-fiddling and data structure generation is fast enough with PyPy, so we haven’t seen a need to optimize that part further.

To showcase our tools, we host public (and open source) websites such as greynir.is for our parsing, named entity recognition and query stack and yfirlestur.is for our spell and grammar checking stack. The server code on these sites is all Python running on PyPy using Flask, wrapped in gunicorn and hosted on nginx. The underlying database is PostgreSQL accessed via SQLAlchemy and psycopg2cffi. This setup has served us well for 6 years and counting, being fast, reliable and having helpful and supporting communities.

As can be inferred from the above, we are avid fans of PyPy and commensurately thankful for the great work by the PyPy team over the years. PyPy has enabled us to use Python for a larger part of our toolset than CPython alone would have supported, and its smooth integration with C/C++ through CFFI has helped us attain a better tradeoff between performance and programmer productivity in our projects. We wish for PyPy a great and bright future and also look forward to exciting related developments on the horizon, such as HPy.