Re: Linux 4.9-rc6

[Eric Dumazet]

On Sun, 2016-11-20 at 14:05 -0800, Linus Torvalds wrote:

> That said, nothing particular is bothering me all that much, but we've
> had some of the VMALLOC_STACK fixups continue to trickle in, so I
> worry that we're not quite done there yet. And let's see what
> Thorsten's regression list looks like next week. So no decision yet,
> it could still go either way.

Hosts with ~100,000 threads have an issue with /prov/vmallocinfo

It can take about 800 usec to skip over ~100,000 struct vmap_area
in s_start(), while holding vmap_area_lock spinlock, and therefore
blocking fork()/pthread_create().

I presume we can not switch to the rbtree (vmap_area_root)
for /proc/vmallocinfo, because this file is seek-able, right ?