On Tue, Apr 04, 2023 at 01:57:41PM +0000, Joel Fernandes wrote: > On Thu, Mar 30, 2023 at 03:47:02PM -0700, Paul E. McKenney wrote: > > Hello! > > > > This post-RFC series shrinks the srcu_struct structure to the bare minimum > > required to support SRCU readers, relegating the remaining fields to a new > > srcu_usage structure. Statically allocated srcu_struct structures created > > by DEFINE_SRCU() and DEFINE_STATIC_SRCU() have statically allocated > > srcu_usage structures, but those required for dynamically allocated > > srcu_struct structures that are initialized using init_srcu_struct() > > are dynamically allocated. > > > > The results is a reduction in the size of an srcu_struct structure from > > a couple hundred bytes to just 24 bytes on x86_64 systems. This can be > > helpful when SRCU readers are used in a fastpath for which the srcu_struct > > structure must be embedded in another structure, and especially where > > that fastpath also needs to access fields both before and after the > > srcu_struct structure. > > > > This series takes baby steps, in part because breaking SRCU means that > > you get absolutely no console output. Yes, I did learn this the hard way. > > Why do you ask? ;-) > > > > Here are those baby steps: > > > > 1. rcu-tasks: Fix warning for unused tasks_rcu_exit_srcu. > > > > 2. Add whitespace to __SRCU_STRUCT_INIT() & __DEFINE_SRCU(). > > > > 3. Use static init for statically allocated in-module srcu_struct. > > > > 4. Begin offloading srcu_struct fields to srcu_update. > > > > 5. Move ->level from srcu_struct to srcu_usage. > > > > 6. Move ->srcu_size_state from srcu_struct to srcu_usage. > > > > 7. Move ->srcu_cb_mutex from srcu_struct to srcu_usage. > > > > 8. Move ->lock initialization after srcu_usage allocation. > > > > 9. Move ->lock from srcu_struct to srcu_usage. > > > > 10. Move ->srcu_gp_mutex from srcu_struct to srcu_usage. > > > > 11. Move grace-period fields from srcu_struct to srcu_usage. > > > > 12. Move heuristics fields from srcu_struct to srcu_usage. > > > > 13. Move ->sda_is_static from srcu_struct to srcu_usage. > > > > 14. Move srcu_barrier() fields from srcu_struct to srcu_usage. > > > > 15. Move work-scheduling fields from srcu_struct to srcu_usage. > > > > 16. Check for readers at module-exit time. > > > > 17. Fix long lines in srcu_get_delay(). > > > > 18. Fix long lines in cleanup_srcu_struct(). > > > > 19. Fix long lines in srcu_gp_end(). > > > > 20. Fix long lines in srcu_funnel_gp_start(). > > > > Changes since the RFC series: > > https://lore.kernel.org/all/3db82572-f156-4a5d-b711-841aa28bd996@paulmck-laptop/ > > > > 1. Add checks for readers of in-module statically allocated > > srcu_struct structures persisting past module unload. > > > > 2. Apply Tested-by tags. > > > > 3. Apply feedback from "Zhang, Qiang1" and kernel test robot, > > perhaps most notably getting rid of memory leaks and improving > > the handling of statically allocated srcu_struct structures > > defined within modules. > > > > 4. Drop the commit removing extraneous parentheses given the desire > > to push this into the v6.4 merge window, the fact that this > > commit generates conflicts with other v6.4 RCU commits, and the > > low value of this commit. It therefore remains in the v6.5 pile. > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > b/include/linux/notifier.h | 5 > > b/include/linux/srcutiny.h | 6 > > b/include/linux/srcutree.h | 28 +- > > b/kernel/rcu/rcu.h | 6 > > b/kernel/rcu/srcutree.c | 19 + > > b/kernel/rcu/tasks.h | 2 > > include/linux/srcutree.h | 123 ++++++----- > > kernel/rcu/srcutree.c | 495 +++++++++++++++++++++++---------------------- > > 8 files changed, 370 insertions(+), 314 deletions(-) > > It looks good on my ARM64 board: > Tested-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Thank you! I will apply on my rebase later today. > Output of run: > > tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2h --configs SRCU-P SRCU-N SRCU-T SRCU-U --trust-make > SRCU-N ------- 204135 GPs (28.3521/s) [srcu: g1765408 f0x0 total-gps=1765408] n_max_cbs: 150000 > :CONFIG_HYPERVISOR_GUEST=y: improperly set > :CONFIG_KVM_GUEST=y: improperly set > SRCU-P ------- 105511 GPs (14.6543/s) [srcud: g884128 f0x0 total-gps=884128] n_max_cbs: 150000 > :CONFIG_HYPERVISOR_GUEST=y: improperly set > :CONFIG_KVM_GUEST=y: improperly set > SRCU-T ------- 334055 GPs (46.3965/s) [srcu: g2638072 f0x0 total-gps=2638072] n_max_cbs: 50000 > :CONFIG_HYPERVISOR_GUEST=y: improperly set > :CONFIG_KVM_GUEST=y: improperly set > :CONFIG_SMP: improperly set > :CONFIG_TINY_SRCU=y: improperly set > SRCU-U ------- 292738 GPs (40.6581/s) [srcud: g2349416 f0x0 total-gps=2349416] n_max_cbs: 50000 > :CONFIG_HYPERVISOR_GUEST=y: improperly set > :CONFIG_KVM_GUEST=y: improperly set > :CONFIG_SMP: improperly set > :CONFIG_TINY_SRCU=y: improperly set > 1 runs with build errors. > > That "build error" is actually perl doing this: > > perl: warning: Please check that your locale settings: > perl: warning: Falling back to the standard locale ("C"). > > I think its harmless and the test did fine. It is just that my chroot is > missing some packages (I have run into this warning before). Frederic ran into some similar messages where the scripts implicitly assumed en_us locale, but his warnings were specific to rcutorture. > The "improperly set" thingies are perhaps Kconfig on ARM64 setting some KVM > options slightly differently. I have seen that before as well on this board. Agreed, and one of the things on the long list is to allow arch-specific settings for those options. The CONFIG_SMP warnings are interesting, though. Does arm64 disallow !SMP builds? ;-) Thanx, Paul
