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[Python-Dev] The untuned tunable parameter ARENA_SIZE

INADA Naoki songofacandy at gmail.com
Thu Jun 1 05:21:55 EDT 2017 
Thanks for detailed info.

But I don't think it's a big problem.
Arenas are returned to system by chance.  So other processes
shouldn't relying to it.

And I don't propose to stop returning arena to system.
I just mean per pool (part of arena) MADV_DONTNEED can reduce RSS.

If we use very large arena, or stop returning arena to system,
it can be problem.

Regards,

On Thu, Jun 1, 2017 at 6:05 PM, Siddhesh Poyarekar <siddhesh at gotplt.org> wrote:
> On Thursday 01 June 2017 01:53 PM, INADA Naoki wrote:
>> * On Linux, madvice(..., MADV_DONTNEED) can be used.
>
> madvise does not reduce the commit charge in the Linux kernel, so in
> high consumption scenarios (and where memory overcommit is disabled or
> throttled) you'll see programs dying with OOM despite the MADV_DONTNEED.
>  The way we solved it in glibc was to use mprotect to drop PROT_READ and
> PROT_WRITE in blocks that we don't need when we detect that the system
> is not configured to overcommit (using /proc/sys/vm/overcommit_memory).
> You'll need to fix the protection again though if you want to reuse the
> block.
>
> Siddhesh
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