Messages in this thread Patch in this message | | | From | Ankur Arora <> | Subject | Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling | Date | Thu, 15 Feb 2024 13:24:59 -0800 |
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Paul E. McKenney <paulmck@kernel.org> writes:
> On Wed, Feb 14, 2024 at 07:45:18PM -0800, Paul E. McKenney wrote: >> On Wed, Feb 14, 2024 at 06:03:28PM -0800, Ankur Arora wrote: >> > >> > Paul E. McKenney <paulmck@kernel.org> writes: >> > >> > > On Mon, Feb 12, 2024 at 09:55:24PM -0800, Ankur Arora wrote: >> > >> Hi, >> > >> >> > >> This series adds a new scheduling model PREEMPT_AUTO, which like >> > >> PREEMPT_DYNAMIC allows dynamic switching between a none/voluntary/full >> > >> preemption model. However, unlike PREEMPT_DYNAMIC, it doesn't depend >> > >> on explicit preemption points for the voluntary models. >> > >> >> > >> The series is based on Thomas' original proposal which he outlined >> > >> in [1], [2] and in his PoC [3]. >> > >> >> > >> An earlier RFC version is at [4]. >> > > >> > > This uncovered a couple of latent bugs in RCU due to its having been >> > > a good long time since anyone built a !SMP preemptible kernel with >> > > non-preemptible RCU. I have a couple of fixes queued on -rcu [1], most >> > > likely for the merge window after next, but let me know if you need >> > > them sooner. >> > >> > Thanks. As you can probably tell, I skipped out on !SMP in my testing. >> > But, the attached diff should tide me over until the fixes are in. >> >> That was indeed my guess. ;-) >> >> > > I am also seeing OOM conditions during rcutorture testing of callback >> > > flooding, but I am still looking into this. >> > >> > That's on the PREEMPT_AUTO && PREEMPT_VOLUNTARY configuration? >> >> On two of the PREEMPT_AUTO && PREEMPT_NONE configurations, but only on >> two of them thus far. I am running a longer test to see if this might >> be just luck. If not, I look to see what rcutorture scenarios TREE10 >> and TRACE01 have in common. > > And still TRACE01 and TREE10 are hitting OOMs, still not seeing what > sets them apart. I also hit a grace-period hang in TREE04, which does > CONFIG_PREEMPT_VOLUNTARY=y along with CONFIG_PREEMPT_AUTO=y. Something > to dig into more.
So, the only PREEMPT_VOLUNTARY=y configuration is TREE04. I wonder if you would continue to hit the TREE04 hang with CONFIG_PREEMTP_NONE=y as well? (Just in the interest of minimizing configurations.)
--- diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 b/tools/testing/selftests/rcutorture/configs/rcu/TREE04 index 9ef845d54fa4..819cff9113d8 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04 @@ -1,7 +1,7 @@ CONFIG_SMP=y CONFIG_NR_CPUS=8 -CONFIG_PREEMPT_NONE=n -CONFIG_PREEMPT_VOLUNTARY=y +CONFIG_PREEMPT_NONE=y +CONFIG_PREEMPT_VOLUNTARY=n CONFIG_PREEMPT_AUTO=y CONFIG_PREEMPT=n CONFIG_PREEMPT_DYNAMIC=n
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