| Message ID | 20250331210314.590622-4-paulmck@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,01/12] rcutorture: Make srcu_lockdep.sh check kernel Kconfig | expand |
On 2025-03-31 14:03:06 [-0700], Paul E. McKenney wrote: > The torture.sh --do-rt command-line parameter is intended to mimic -rt > kernels. Now that CONFIG_PREEMPT_RT is upstream, this commit makes this > mimicking more precise. > > Note that testing of RCU priority boosting is disabled in favor > of forward-progress testing of RCU callbacks. If it turns out to be > possible to make kernels built with CONFIG_PREEMPT_RT=y to tolerate > testing of both, both will be enabled. Not sure what you point at here: You can build a PREEMPT_RT kernel and RCU boosting is enabled by default. You could disable it if needed. Config wise you set CONFIG_PREEMPT_LAZY=n but in general CONFIG_PREEMPT_LAZY=y should be used if possible. The preemption while holding a sleeping spinlock is somehow bad for performance if a lot of threads ask for it. But then it probably doesn't matter for testing. You do set rcupdate.rcu_normal and rcupdate.rcu_expedited but RT has rcu_normal_after_boot set by default. Not sure if this makes any difference but I *think* that normal wins here. > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Sebastian
On Wed, Apr 02, 2025 at 09:42:11AM +0200, Sebastian Andrzej Siewior wrote: > On 2025-03-31 14:03:06 [-0700], Paul E. McKenney wrote: > > The torture.sh --do-rt command-line parameter is intended to mimic -rt > > kernels. Now that CONFIG_PREEMPT_RT is upstream, this commit makes this > > mimicking more precise. > > > > Note that testing of RCU priority boosting is disabled in favor > > of forward-progress testing of RCU callbacks. If it turns out to be > > possible to make kernels built with CONFIG_PREEMPT_RT=y to tolerate > > testing of both, both will be enabled. > > Not sure what you point at here: You can build a PREEMPT_RT kernel and > RCU boosting is enabled by default. You could disable it if needed. The issue is not the enabling of RCU priority boosting itself, but instead the rcutorture testing of it. And if it makes you feel better, this problem is now sometimes affecting mainline testing. So maybe rcutorture will need to do only one form of overload testing at a time, maybe using a mutex or some such. > Config wise you set CONFIG_PREEMPT_LAZY=n but in general > CONFIG_PREEMPT_LAZY=y should be used if possible. The preemption while > holding a sleeping spinlock is somehow bad for performance if a lot of > threads ask for it. But then it probably doesn't matter for testing. For general use, agreed. But in this case, I want CONFIG_PREEMPT_RT=y, so I must also end up with CONFIG_PREEMPT_LAZY=n, right? Though to your point, that happens by default, so I don't need to explicitly specify it. Or if the concern is general rcutorture testing of CONFIG_PREEMPT_LAZY=y, that is done by the TREE07 and TREE10 rcutorture scenarios, both of which I run regularly. > You do set rcupdate.rcu_normal and rcupdate.rcu_expedited but RT has > rcu_normal_after_boot set by default. Not sure if this makes any > difference but I *think* that normal wins here. I should definitely align with -rt common practice regardless. Plus rcupdate.rcu_normal_after_boot is set by default by PREEMPT_RT, so there is no need to separately specify it. On the other hand, the variant that does use expedited grace periods needs to explicitly disable rcu_normal_after_boot. Do real-time kernels normally enable NO_HZ_FULL? Or do event-driven real-time workloads prefer NO_HZ_IDLE? I am currently guessing NO_HZ_IDLE. (I test NO_HZ_FULL in conjunction with expedited grace periods in the second run.) Please see incremental patch below, which I am testing. Thanx, Paul > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ------------------------------------------------------------------------ diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh index ed43aea91c7d9..6d1a84f3f6315 100755 --- a/tools/testing/selftests/rcutorture/bin/torture.sh +++ b/tools/testing/selftests/rcutorture/bin/torture.sh @@ -481,13 +481,13 @@ then # -rt doesn't like its interaction with testing of callback # flooding. - # With all post-boot grace periods forced to normal. - torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcupdate.rcu_normal=1" - torture_set "rcurttorture" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_LAZY=n CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y" --trust-make + # With all post-boot grace periods forced to normal (default for PREEMPT_RT). + torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcutorture.preempt_duration=0" + torture_set "rcurttorture" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y CONFIG_HZ_PERIODIC=n CONFIG_NO_HZ_IDLE=y" --trust-make # With all post-boot grace periods forced to expedited. - torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcupdate.rcu_expedited=1" - torture_set "rcurttorture-exp" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_LAZY=n CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y" --trust-make + torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcupdate.rcu_normal_after_boot=0 rcupdate.rcu_expedited=1 rcutorture.preempt_duration=0" + torture_set "rcurttorture-exp" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y CONFIG_HZ_PERIODIC=n CONFIG_NO_HZ_FULL=y" --trust-make fi if test "$do_rcu_rust" = "yes"
diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh index 0447c4a00cc4d..9cabe505585ea 100755 --- a/tools/testing/selftests/rcutorture/bin/torture.sh +++ b/tools/testing/selftests/rcutorture/bin/torture.sh @@ -448,13 +448,17 @@ fi if test "$do_rt" = "yes" then + # In both runs, disable testing of RCU priority boosting because + # -rt doesn't like its interaction with testing of callback + # flooding. + # With all post-boot grace periods forced to normal. - torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcupdate.rcu_normal=1" - torture_set "rcurttorture" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --trust-make + torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcupdate.rcu_normal=1" + torture_set "rcurttorture" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_LAZY=n CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y" --trust-make # With all post-boot grace periods forced to expedited. - torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcupdate.rcu_expedited=1" - torture_set "rcurttorture-exp" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --trust-make + torture_bootargs="rcupdate.rcu_cpu_stall_suppress_at_boot=1 torture.disable_onoff_at_boot rcupdate.rcu_task_stall_timeout=30000 rcutorture.test_boost=0 rcupdate.rcu_expedited=1" + torture_set "rcurttorture-exp" tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration "$duration_rcutorture" --configs "TREE03" --kconfig "CONFIG_PREEMPT_LAZY=n CONFIG_PREEMPT_RT=y CONFIG_EXPERT=y" --trust-make fi if test "$do_srcu_lockdep" = "yes"
The torture.sh --do-rt command-line parameter is intended to mimic -rt kernels. Now that CONFIG_PREEMPT_RT is upstream, this commit makes this mimicking more precise. Note that testing of RCU priority boosting is disabled in favor of forward-progress testing of RCU callbacks. If it turns out to be possible to make kernels built with CONFIG_PREEMPT_RT=y to tolerate testing of both, both will be enabled. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- tools/testing/selftests/rcutorture/bin/torture.sh | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)