| Message ID | 20240407090558.3395-1-jiangshanlai@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | rcu/x86: Use per-cpu rcu preempt count | expand |
On Sun, Apr 07, 2024 at 05:05:47PM +0800, Lai Jiangshan wrote: > From: Lai Jiangshan <jiangshan.ljs@antgroup.com> > > > Changed from v1: > Merge thunk_64.S and thunk_32.S into thunk.S > Add missing #ifdef in arch/x86/kernel/cpu/common.c > > X86 can access percpu data in a single instruction. > > Use per-cpu rcu preempt count and make it able to be inlined. > > patch 1-8: prepare > patch 9-11: implement PCPU_RCU_PREEMPT_COUNT > > Cc: "Paul E. McKenney" <paulmck@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Frederic Weisbecker <frederic@kernel.org> Hello, Lai! This is really cool stuff, thank you!!! Two big questions remain: (1) What system-level net performance benefit is there, taking the increased context-switch overhead into account and (2) Are the scheduler maintainers on board with these changes? On #1, I do well recall your ca. 2019 points about the improved code generated, but I have seen cases where improved code actually ran more slowly. My guess is that you have the best chance of seeing system-level benefits on low-end x86 platforms, perhaps the old Atom or Celeron systems. The rcuref module provides a good way of doing microbenchmarks, which would be a good start. Other metrics that might help include overall kernel code size. On #2, good data for #1 would help greatly. Thoughts? Thanx, Paul > Lai Jiangshan (11): > lib: Use rcu_preempt_depth() to replace current->rcu_read_lock_nesting > rcu: Move rcu_preempt_depth_set() to rcupdate.h > rcu: Reorder tree_exp.h after tree_plugin.h > rcu: Add macros set_rcu_preempt_special() and > clear_rcu_preempt_special() > rcu: Make rcu_read_unlock_special() global > rcu: Rename marco __LINUX_RCU_H to __KERNEL_RCU_H > sched/core: Add rcu_preempt_switch() > x86/entry: Merge thunk_64.S and thunk_32.S into thunk.S > rcu: Implement PCPU_RCU_PREEMPT_COUNT framework > x86/rcu: Add rcu_preempt_count > x86/rcu: Add THUNK rcu_read_unlock_special_thunk > > arch/x86/Kconfig | 1 + > arch/x86/entry/Makefile | 2 +- > arch/x86/entry/{thunk_64.S => thunk.S} | 5 ++ > arch/x86/entry/thunk_32.S | 18 ---- > arch/x86/include/asm/current.h | 3 + > arch/x86/include/asm/rcu_preempt.h | 109 +++++++++++++++++++++++++ > arch/x86/kernel/cpu/common.c | 4 + > include/linux/rcupdate.h | 36 ++++++++ > kernel/rcu/Kconfig | 8 ++ > kernel/rcu/rcu.h | 15 +++- > kernel/rcu/tree.c | 2 +- > kernel/rcu/tree_exp.h | 2 +- > kernel/rcu/tree_plugin.h | 41 ++++++---- > kernel/sched/core.c | 2 + > lib/locking-selftest.c | 6 +- > 15 files changed, 212 insertions(+), 42 deletions(-) > rename arch/x86/entry/{thunk_64.S => thunk.S} (72%) > delete mode 100644 arch/x86/entry/thunk_32.S > create mode 100644 arch/x86/include/asm/rcu_preempt.h > > > base-commit: f2f80ac809875855ac843f9e5e7480604b5cbff5 > -- > 2.19.1.6.gb485710b >
From: Lai Jiangshan <jiangshan.ljs@antgroup.com> Changed from v1: Merge thunk_64.S and thunk_32.S into thunk.S Add missing #ifdef in arch/x86/kernel/cpu/common.c X86 can access percpu data in a single instruction. Use per-cpu rcu preempt count and make it able to be inlined. patch 1-8: prepare patch 9-11: implement PCPU_RCU_PREEMPT_COUNT Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <frederic@kernel.org> Lai Jiangshan (11): lib: Use rcu_preempt_depth() to replace current->rcu_read_lock_nesting rcu: Move rcu_preempt_depth_set() to rcupdate.h rcu: Reorder tree_exp.h after tree_plugin.h rcu: Add macros set_rcu_preempt_special() and clear_rcu_preempt_special() rcu: Make rcu_read_unlock_special() global rcu: Rename marco __LINUX_RCU_H to __KERNEL_RCU_H sched/core: Add rcu_preempt_switch() x86/entry: Merge thunk_64.S and thunk_32.S into thunk.S rcu: Implement PCPU_RCU_PREEMPT_COUNT framework x86/rcu: Add rcu_preempt_count x86/rcu: Add THUNK rcu_read_unlock_special_thunk arch/x86/Kconfig | 1 + arch/x86/entry/Makefile | 2 +- arch/x86/entry/{thunk_64.S => thunk.S} | 5 ++ arch/x86/entry/thunk_32.S | 18 ---- arch/x86/include/asm/current.h | 3 + arch/x86/include/asm/rcu_preempt.h | 109 +++++++++++++++++++++++++ arch/x86/kernel/cpu/common.c | 4 + include/linux/rcupdate.h | 36 ++++++++ kernel/rcu/Kconfig | 8 ++ kernel/rcu/rcu.h | 15 +++- kernel/rcu/tree.c | 2 +- kernel/rcu/tree_exp.h | 2 +- kernel/rcu/tree_plugin.h | 41 ++++++---- kernel/sched/core.c | 2 + lib/locking-selftest.c | 6 +- 15 files changed, 212 insertions(+), 42 deletions(-) rename arch/x86/entry/{thunk_64.S => thunk.S} (72%) delete mode 100644 arch/x86/entry/thunk_32.S create mode 100644 arch/x86/include/asm/rcu_preempt.h base-commit: f2f80ac809875855ac843f9e5e7480604b5cbff5