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| /openbmc/linux/Documentation/admin-guide/sysctl/ |
| H A D | kernel.rst | diff e80d89380c5a8553f208d002ee0f7877ed08eb6c Thu Oct 31 23:04:38 CDT 2019 Masanari Iida <standby24x7@gmail.com> docs: admin-guide: Remove threads-max auto-tuning
Since following path was merged in 5.4-rc3,
auto-tuning feature in threads-max does not exist any more.
Fix the admin-guide document as is.
kernel/sysctl.c: do not override max_threads provided by userspace
b0f53dbc4bc4c371f38b14c391095a3bb8a0bb40
Fixes: b0f53dbc4bc4 ("kernel/sysctl.c: do not override max_threads provided by userspace")
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff 73eb802ad97f814aa86d83cfd1d139cadbb4f0fb Thu Oct 31 23:04:37 CDT 2019 Masanari Iida <standby24x7@gmail.com> docs: admin-guide: Fix min value of threads-max in kernel.rst
Since following patch was merged 5.4-rc3, minimum value for
threads-max changed to 1.
kernel/sysctl.c: do not override max_threads provided by userspace
b0f53dbc4bc4c371f38b14c391095a3bb8a0bb40
Fixes: b0f53dbc4bc4 ("kernel/sysctl.c: do not override max_threads provided by userspace")
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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| /openbmc/linux/kernel/ |
| H A D | fork.c | diff b0f53dbc4bc4c371f38b14c391095a3bb8a0bb40 Sun Oct 06 19:58:19 CDT 2019 Michal Hocko <mhocko@suse.com> kernel/sysctl.c: do not override max_threads provided by userspace
Partially revert 16db3d3f1170 ("kernel/sysctl.c: threads-max observe
limits") because the patch is causing a regression to any workload which
needs to override the auto-tuning of the limit provided by kernel.
set_max_threads is implementing a boot time guesstimate to provide a
sensible limit of the concurrently running threads so that runaways will
not deplete all the memory. This is a good thing in general but there
are workloads which might need to increase this limit for an application
to run (reportedly WebSpher MQ is affected) and that is simply not
possible after the mentioned change. It is also very dubious to
override an admin decision by an estimation that doesn't have any direct
relation to correctness of the kernel operation.
Fix this by dropping set_max_threads from sysctl_max_threads so any
value is accepted as long as it fits into MAX_THREADS which is important
to check because allowing more threads could break internal robust futex
restriction. While at it, do not use MIN_THREADS as the lower boundary
because it is also only a heuristic for automatic estimation and admin
might have a good reason to stop new threads to be created even when
below this limit.
This became more severe when we switched x86 from 4k to 8k kernel
stacks. Starting since 6538b8ea886e ("x86_64: expand kernel stack to
16K") (3.16) we use THREAD_SIZE_ORDER = 2 and that halved the auto-tuned
value.
In the particular case
3.12
kernel.threads-max = 515561
4.4
kernel.threads-max = 200000
Neither of the two values is really insane on 32GB machine.
I am not sure we want/need to tune the max_thread value further. If
anything the tuning should be removed altogether if proven not useful in
general. But we definitely need a way to override this auto-tuning.
Link: http://lkml.kernel.org/r/20190922065801.GB18814@dhcp22.suse.cz
Fixes: 16db3d3f1170 ("kernel/sysctl.c: threads-max observe limits")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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