On 2021-12-15 17:56:03 [+0100], Michal Hocko wrote: > On Wed 15-12-21 17:47:54, Sebastian Andrzej Siewior wrote: > > On 2021-12-13 11:08:26 [+0100], Michal Hocko wrote: > > > On Fri 10-12-21 16:22:01, Sebastian Andrzej Siewior wrote: > > > [...] > > > I am sorry but I didn't get to read and digest the rest of the message > > > yet. Let me just point out this > > > > > > > The problematic part here is mem_cgroup_tree_per_node::lock which can > > > > not be acquired with disabled interrupts on PREEMPT_RT. The "locking > > > > scope" is not always clear to me. Also, if it is _just_ the counter, > > > > then we might solve this differently. > > > > > > I do not think you should be losing sleep over soft limit reclaim. This > > > is certainly not something to be used for RT workloads and rather than > > > touching that code I think it makes some sense to simply disallow soft > > > limit with RT enabled (i.e. do not allow to set any soft limit). > > > > Okay. So instead of disabling it entirely you suggest I should take > > another stab at it? Okay. Disabling softlimit, where should I start with > > it? Should mem_cgroup_write() for RES_SOFT_LIMIT always return an error > > or something else? > > Yeah, I would just return an error for RT configuration. If we ever need > to implement that behavior for RT then we can look at specific fixes. Okay. What do I gain by doing this / how do I test this? Is running tools/testing/selftests/cgroup/test_*mem* sufficient to test all corner cases here? > Thanks! Thank you ;) Sebastian
