[Bug 2089789] Re: malloc performance degradation with CPU affinity masks

[Mauricio Faria de Oliveira]

Some snippets (more line breaks for clarity) from
https://sourceware.org/bugzilla/show_bug.cgi?id=30945

	"""
	<...> The deserialization library we used works 10x slower than expected.

	Investigations show that this is due to the arena_get2 function uses
	__get_nprocs_sched instead of __get_nprocs. 

	Without changing core affinity settings, this call returns the real number
	of cores so the upper limit of total arenas is set correctly. 

	However, if a thread is pinned to a core, further malloc calls only sees
	n = 1 because the function returns only schedulable cores.

        Therefore, the maximum number of arenas will be 8 on 64-bit
platforms.

	<...>
	    ./a.out 32 false false
	    ---
	    nr_cpu: 32 pin: no fix: no
	    thread average (ms): 16.233663

	    ./a.out 32 true false
	    ---
	    nr_cpu: 32 pin: yes fix: no
	    thread average (ms): 1360.919047

	<...>
	Fixed on 2.39.
	<...>
	I backported it to 2.34, 2.35, 2.36, 2.37, and 2.38.
	"""

** Bug watch added: Sourceware.org Bugzilla #30945
   https://sourceware.org/bugzilla/show_bug.cgi?id=30945

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https://bugs.launchpad.net/bugs/2089789

Title:
  malloc performance degradation with CPU affinity masks

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Jammy:
  Confirmed

Bug description:
  https://sourceware.org/bugzilla/show_bug.cgi?id=30945

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