On 2022-01-25 15:21:46 [-0800], Andrew Morton wrote: > On Tue, 25 Jan 2022 17:43:33 +0100 Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > > > Hi, > > > > this series is a follow up to the initial RFC > > https://lore.kernel.org/all/20211222114111.2206248-1-bigeasy@xxxxxxxxxxxxx > > > > and aims to enable MEMCG for PREEMPT_RT instead of disabling it. > > > > where it has been suggested that I should try again with memcg instead > > of simply disabling it. > > > > Changes since the RFC: > > - cgroup.event_control / memory.soft_limit_in_bytes is disabled on > > PREEMPT_RT. It is a deprecated v1 feature. Fixing the signal path is > > not worth it. > > > > - The updates to per-CPU counters are usually synchronised by disabling > > interrupts. There are a few spots where assumption about disabled > > interrupts are not true on PREEMPT_RT and therefore preemption is > > disabled. This is okay since the counter are never written from > > in_irq() context. > > > > Patch #2 deals with the counters. > > > > Patch #3 is a follow up to > > https://lkml.kernel.org/r/20211214144412.447035-1-longman@xxxxxxxxxx > > > > Patch #4 restricts the task_obj usage to !PREEMPTION kernels. Based on > > the numbers in > > https://lore.kernel.org/all/YdX+INO9gQje6d0S@xxxxxxxxxxxxx > > This isn't a terribly useful [0/n], sorry. It would be better to have > something self-contained which doesn't require that the reader chase > down increasingly old links and figure out what changed during > successive iterations. I'm sorry. I didn't want to copy the numbers and make the impression of doing the numbers now on -rc1. > > I tested them on CONFIG_PREEMPT_NONE + CONFIG_PREEMPT_RT with the > > tools/testing/selftests/cgroup/* tests. It looked good except for the > > following (which was also there before the patches): > > - test_kmem sometimes complained about: > > not ok 2 test_kmem_memcg_deletion > > Is this a new issue? No, I saw it already on 5.16.0-rc5. > Does this happen with these patches when CONFIG_PREEMPT_RT=n? Yes. The problem reported by the test is independent of the series and RT. > > - test_memcontrol complained always about > > not ok 3 test_memcg_min > > not ok 4 test_memcg_low > > and did not finish. > > Similarly, is this caused by these patches? Is it only triggered under > preempt_rt? No. This happens regardless of these patches and RT. > > - lockdep complains were triggered by test_core and test_freezer (both > > had to run): > > Ditto. Also happens regardless of these patches and RT. It does not happen always so sometimes I had to run test_core and test_freezer a few times until lockdep complained. Sebastian
