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Message-ID: <20250222190623.262689-1-brgerst@gmail.com> Date: Sat, 22 Feb 2025 14:06:12 -0500 From: Brian Gerst <brgerst@...il.com> To: linux-kernel@...r.kernel.org, x86@...nel.org Cc: Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Ard Biesheuvel <ardb@...nel.org>, Uros Bizjak <ubizjak@...il.com>, Brian Gerst <brgerst@...il.com> Subject: [RFC PATCH 00/11] Add a percpu subsection for hot data Add a new percpu subsection for data that is frequently accessed and exclusive to each processor. This is intended to replace the pcpu_hot struct on X86, and is available to all architectures. The one caveat with this approach is that it depends on the linker to effeciently pack data that is smaller than machine word size. The binutils linker does this properly: ffffffff842f6000 D __per_cpu_hot_start ffffffff842f6000 D softirq_pending ffffffff842f6002 D hardirq_stack_inuse ffffffff842f6008 D hardirq_stack_ptr ffffffff842f6010 D __ref_stack_chk_guard ffffffff842f6010 D __stack_chk_guard ffffffff842f6018 D const_cpu_current_top_of_stack ffffffff842f6018 D cpu_current_top_of_stack ffffffff842f6020 D const_current_task ffffffff842f6020 D current_task ffffffff842f6028 D __preempt_count ffffffff842f602c D cpu_number ffffffff842f6030 D this_cpu_off ffffffff842f6038 D __x86_call_depth ffffffff842f6040 D __per_cpu_hot_end The LLVM linker doesn't do as well with packing smaller data objects, causing it to spill over into a second cacheline. Brian Gerst (11): percpu: Introduce percpu hot section x86/preempt: Move preempt count to percpu hot section x86/smp: Move cpu number to percpu hot section x86/retbleed: Move call depth to percpu hot section x86/percpu: Move top_of_stack to percpu hot section x86/percpu: Move current_task to percpu hot section x86/softirq: Move softirq_pending to percpu hot section x86/irq: Move irq stacks to percpu hot section x86/percpu: Remove pcpu_hot x86/stackprotector: Move __stack_chk_guard to percpu hot section x86/smp: Move this_cpu_off to percpu hot section arch/x86/entry/entry_32.S | 4 +-- arch/x86/entry/entry_64.S | 6 ++--- arch/x86/entry/entry_64_compat.S | 4 +-- arch/x86/include/asm/current.h | 35 ++++----------------------- arch/x86/include/asm/hardirq.h | 3 ++- arch/x86/include/asm/irq_stack.h | 12 ++++----- arch/x86/include/asm/nospec-branch.h | 10 +++++--- arch/x86/include/asm/percpu.h | 4 +-- arch/x86/include/asm/preempt.h | 25 ++++++++++--------- arch/x86/include/asm/processor.h | 15 ++++++++++-- arch/x86/include/asm/smp.h | 7 +++--- arch/x86/include/asm/stackprotector.h | 2 +- arch/x86/kernel/asm-offsets.c | 5 ---- arch/x86/kernel/callthunks.c | 3 +++ arch/x86/kernel/cpu/common.c | 17 +++++++------ arch/x86/kernel/dumpstack_32.c | 4 +-- arch/x86/kernel/dumpstack_64.c | 2 +- arch/x86/kernel/head_64.S | 4 +-- arch/x86/kernel/irq.c | 8 ++++++ arch/x86/kernel/irq_32.c | 12 +++++---- arch/x86/kernel/irq_64.c | 6 ++--- arch/x86/kernel/process_32.c | 6 ++--- arch/x86/kernel/process_64.c | 6 ++--- arch/x86/kernel/setup_percpu.c | 7 ++++-- arch/x86/kernel/smpboot.c | 4 +-- arch/x86/kernel/vmlinux.lds.S | 5 +++- arch/x86/lib/retpoline.S | 2 +- include/asm-generic/vmlinux.lds.h | 10 ++++++++ include/linux/percpu-defs.h | 10 ++++++++ kernel/bpf/verifier.c | 4 +-- scripts/gdb/linux/cpus.py | 2 +- 31 files changed, 135 insertions(+), 109 deletions(-) base-commit: 01157ddc58dc2fe428ec17dd5a18cc13f134639f -- 2.48.1
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