I am struggling to run with a large number of threads because OS limits.
https://stackoverflow.com/questions/344203/maximum-number-of-threads-per-process-in-linux
/proc/sys/kernel/threads-max is part of the answer. Also need to set
the ulimit for numprocs so the user can make threads. You may need to
adjust:
/etc/security/limits.conf
But also in fork.c there may be a limitation regarding virtual memory
(or is it the amount of physical memory?) and stack size. Check
set_max_threads. Seems to want to use at maximum 1/8th of the total
ram for thread structures. Involves totalram_pages, is that physical
or virtual RAM pages? Important distinction?
threads = div64_u64((u64) totalram_pages * (u64) PAGE_SIZE,
(u64) THREAD_SIZE * 8UL);
You can get page size via getconf PAGE_SIZE. It looks like
THREAD_SIZE is defined to be 2x the PAGE_SIZE (because
THREAD_ORDER?)?
Actually, THREAD_ORDER, for 64bit linux, is set to 2, so
THREAD_SIZE is 4x the PAGE_SIZE.
So looks like it might be 1/16th of the pages can be set aside for threads?
vmstat -s gives you VM stats, like the number of pages?
vmstat gives me the amount of total memory. That's the numerator of the
equation. Then I divide by 8 * THREAD_SIZE = 8 * (2 * PAGE_SIZE).
Indeed, dividing by 32 is gives me 7925...
Fuck.
- https://github.com/torvalds/linux/blob/master/kernel/fork.c
- Where limit is enforced.
- https://github.com/torvalds/linux/blob/master/mm/page_alloc.c
- Where
totalram_pagesis defined but not helpful :-(
- Where
- https://elixir.bootlin.com/linux/v3.1/source/arch/x86/include/asm/page_64_types.h#L5
- https://github.com/torvalds/linux/blob/a5532439ebab93e47784effb96aafa7d7ba4b760/arch/x86/include/asm/page_64_types.h