On Thu, May 23, 2019 at 5:15 PM Steve Dower <steve.do...@python.org> wrote:
> On 23May2019 0542, Inada Naoki wrote: > > 1. perf shows 95% of CPU time is eaten by _PyObject_Free, not kernel > space. > > 2. This loop is cleary hot: > > > https://github.com/python/cpython/blob/51aa35e9e17eef60d04add9619fe2a7eb938358c/Objects/obmalloc.c#L1816-L1819 > > > > I can attach the process by gdb and I confirmed many arenas have > > same nfreepools. > > It's relatively easy to test replacing our custom allocators with the > system ones, yes? Can we try those to see whether they have the same > characteristic? > > Given the relative amount of investment over the last 19 years [1], I > wouldn't be surprised if most system ones are at least as good for our > needs now. Certainly Windows HeapAlloc has had serious improvements in > that time to help with fragmentation and small allocations. > FYI, and I've mentioned this at PyCon to a few people (might've been you, Steve, I don't remember) -- but at Google we've experimented with disabling obmalloc when using TCMalloc (a faster and thread-aware malloc, which makes a huge difference within Google when dealing with multi-threaded C++ libraries), both using the usual Python benchmarks and real-world code with real-world workloads (a core part of YouTube, for example), all on Linux. There's still a significant benefit to using obmalloc when using glibc's malloc, and also a noticeable benefit when using TCMalloc. There are certainly cases where it doesn't matter much, and there may even be cases where the overhead of obmalloc isn't worth it, but I do believe it's still a firm net benefit. > > Cheers, > Steve > > [1]: > > https://github.com/python/cpython/blob/51aa35e9e17eef60d04add9619fe2a7eb938358c/Objects/obmalloc.c#L769 > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/thomas%40python.org > -- Thomas Wouters <tho...@python.org> Hi! I'm an email virus! Think twice before sending your email to help me spread!
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