Andrew, do you want me to send the patch or you can grab it from here? On Sun 22-09-19 16:24:10, Eric W. Biederman wrote: > Michal Hocko <mho...@kernel.org> writes: > > > From 711000fdc243b6bc68a92f9ef0017ae495086d39 Mon Sep 17 00:00:00 2001 > > From: Michal Hocko <mho...@suse.com> > > Date: Sun, 22 Sep 2019 08:45:28 +0200 > > Subject: [PATCH] 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. > > > > Fixes: 16db3d3f1170 ("kernel/sysctl.c: threads-max observe limits") > > Cc: stable > > Signed-off-by: Michal Hocko <mho...@suse.com> > Reviewed-by: "Eric W. Biederman" <ebied...@xmission.com>
Thanks Eric. > > --- > > kernel/fork.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/fork.c b/kernel/fork.c > > index 2852d0e76ea3..ef865be37e98 100644 > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -2929,7 +2929,7 @@ int sysctl_max_threads(struct ctl_table *table, int > > write, > > struct ctl_table t; > > int ret; > > int threads = max_threads; > > - int min = MIN_THREADS; > > + int min = 1; > > int max = MAX_THREADS; > > > > t = *table; > > @@ -2941,7 +2941,7 @@ int sysctl_max_threads(struct ctl_table *table, int > > write, > > if (ret || !write) > > return ret; > > > > - set_max_threads(threads); > > + max_threads = threads; > > > > return 0; > > } > > -- > > 2.20.1 -- Michal Hocko SUSE Labs