more sysctl values needed to be capable for more threads

[Nobuto Murata]

In bug #1366598, sysctl support and kernel.pid_max=2097152 by default have been implemented. However it turned out that more sysctl default change is needed in some high density deployment, especially vm.max_map_count and kernel.threads-max.

[Nobuto Murata (nobuto)]

TESTCASE

With a patched stress-ng package: https://launchpad.net/~nobuto/+archive/ubuntu/pthread/+files/stress-ng_0.03.15-1ppa1_amd64.deb
and 8GB memory nodes.

$ sudo stress-ng --pthread 1 --pthread-max 60000 --pthread-ops 60000
$ sudo stress-ng --pthread 1 --pthread-max 256000 --pthread-ops 256000

[Current result]
$ sudo stress-ng --pthread 1 --pthread-max 60000 --pthread-ops 60000
stress-ng: info: [179250] defaulting to a 86400 second run per stressor
stress-ng: info: [179250] dispatching hogs: 1 pthread
stress-ng: error: [179251] stress-ng-pthread: pthread create failed, errno=12 (Cannot allocate memory)
stress-ng: info: [179250] successful run completed in 2.45s

$ sudo stress-ng --pthread 1 --pthread-max 256000 --pthread-ops 256000
stress-ng: info: [146499] defaulting to a 86400 second run per stressor
stress-ng: info: [146499] re-adjusting maximum threads to soft limit of 63803
stress-ng: info: [146499] dispatching hogs: 1 pthread
stress-ng: error: [146500] stress-ng-pthread: pthread create failed, errno=12 (Cannot allocate memory)
stress-ng: info: [146499] successful run completed in 2.02s

-> pthread create failed, errno=12 (Cannot allocate memory)

[result with new defaults]
$ sudo stress-ng --pthread 1 --pthread-max 60000 --pthread-ops 60000
stress-ng: info: [15587] defaulting to a 86400 second run per stressor
stress-ng: info: [15587] dispatching hogs: 1 pthread
stress-ng: info: [15587] successful run completed in 5.86s

$ sudo stress-ng --pthread 1 --pthread-max 256000 --pthread-ops 256000
stress-ng: info: [185128] defaulting to a 86400 second run per stressor
stress-ng: info: [185128] re-adjusting maximum threads to soft limit of 63803
stress-ng: info: [185128] dispatching hogs: 1 pthread
stress-ng: info: [185128] successful run completed in 20.96s

-> no pthread creation error