[Python-Dev] obmalloc mmap/munmap thrashing (original) (raw)

Alexander Walters tritium-list at sdamon.com
Thu Apr 21 17:55:48 EDT 2016

...is that a typo for 2.7.11?

On 4/21/2016 17:44, Neil Schemenauer wrote:

I was running Python 2.4.11 under strace and I noticed some odd looking system calls:

mmap(NULL, 262144, PROTREAD|PROTWRITE, MAPPRIVATE|MAPANONYMOUS, -1, 0) = 0x7f9848681000 munmap(0x7f9848681000, 262144) = 0 mmap(NULL, 262144, PROTREAD|PROTWRITE, MAPPRIVATE|MAPANONYMOUS, -1, 0) = 0x7f9848681000 munmap(0x7f9848681000, 262144) = 0 [... repeated a number of times ...] Looking at obmalloc.c, there doesn't seem to be any high/low watermark (hysteresis) associated with unallocating arenas. Is that true? If so, does it seem prudent to implement something to avoid this behavior? It seems potentially expensive if you program is running just at the threshold of needing another arena.

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