EXPERIMENTAL This is an experimental pull request and a proof of concept. mimalloc integration is in a very early stage.

Vendor and hook up mimalloc. The PR only replaces raw memory allocator and Python's internal obmalloc with mimalloc. It does not use any of the advanced features of mimalloc such as heaps.

• Includes mimalloc v1.7.1 and additional fixes
• --with-mimalloc=yes by default (for testing)
• --with-pymalloc=no by default
• --with-freelists=yes

mimalloc requires C11 <stdatomic.h> on POSIX platforms to provide atomic operations such as CAS. GCC on RHEL 7 / CentOS 7 is too old. GCC 4.9 and clang 3.6 seem to be minimum versions. Users need install Red Hat Developer Toolset 10.0 from Software Collections. The CentOS 7-based manylinux2014 container image comes with GCC 10.2 pre-installed.

related mimalloc tickets

• microsoft/mimalloc#467
• microsoft/mimalloc#468
• microsoft/mimalloc#472
• microsoft/mimalloc#474
• microsoft/mimalloc#475

Initial benchmarks

Initial benchmarks should be taken with a big grain of salt. It seems like mimalloc is in the same ballpark as libc malloc + obmalloc with slightly better performance in some cases. I haven't measured memory consumption yet.

with mimalloc, without pymalloc, without freelists

In general about same performance, with some benchmarks 7% faster to 12% slower, https://gist.github.com/pablogsal/33fce1cbe5f908c1d85cae5d678f50a6

with mimalloc, without pymalloc, with freelists

In general 2% speedup, with some benchmarks 9% faster to 6% slower, https://gist.github.com/pablogsal/8027937b71cd30f17aaaa5ef7c885d3e

debug output

>>> sys._debugmallocstats()
mimalloc (version: 171)
heap stats:     peak      total      freed    current       unit      count  
  reserved:   256.0 mb   256.0 mb       0 b    256.0 mb       1 b              not all freed!
 committed:    20.0 mb    20.0 mb       0 b     20.0 mb       1 b              not all freed!
     reset:     1.0 mb     1.0 mb       0 b      1.0 mb       1 b              not all freed!
   touched:       0 b        0 b    932.3 kb  -932.3 kb       1 b              ok
  segments:       5          5          1          4                           not all freed!
-abandoned:       0          0          0          0                           ok
   -cached:       0          0          0          0                           ok
     pages:      94        123         29         94                           not all freed!
-abandoned:       0          0          0          0                           ok
 -extended:       0   
 -noretire:       0   
     mmaps:       0   
   commits:      69   
   threads:       0          0          0          0                           ok
  searches:     0.0 avg
numa nodes:       1
   elapsed:       5.572 s
   process: user: 0.073 s, system: 0.007 s, faults: 0, rss: 11.9 mb, commit: 20.0 mb
...