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Message-Id: <20130910130811.507933095@infradead.org> Date: Tue, 10 Sep 2013 15:08:11 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...nel.org> Cc: Andi Kleen <ak@...ux.intel.com>, Peter Anvin <hpa@...or.com>, Mike Galbraith <bitbucket@...ine.de>, Thomas Gleixner <tglx@...utronix.de>, Arjan van de Ven <arjan@...ux.intel.com>, Frederic Weisbecker <fweisbec@...il.com>, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, Peter Zijlstra <peterz@...radead.org> Subject: [PATCH 0/7] preempt_count rework -v2 These patches optimize preempt_enable by firstly folding the preempt and need_resched tests into one -- this should work for all architectures. And secondly by providing per-arch preempt_count implementations; with x86 using per-cpu preempt_count for fastest access. These patches have been boot tested on CONFIG_PREEMPT=y x86_64 and survive building a x86_64-defconfig kernel. kernel/sched/core.c:kick_process() now looks like: ffffffff8106f3f0 <kick_process>: ffffffff8106f3f0: 55 push %rbp ffffffff8106f3f1: 65 ff 04 25 e0 b7 00 incl %gs:0xb7e0 ffffffff8106f3f8: 00 ffffffff8106f3f9: 48 89 e5 mov %rsp,%rbp ffffffff8106f3fc: 48 8b 47 08 mov 0x8(%rdi),%rax ffffffff8106f400: 8b 50 18 mov 0x18(%rax),%edx ffffffff8106f403: 65 8b 04 25 1c b0 00 mov %gs:0xb01c,%eax ffffffff8106f40a: 00 ffffffff8106f40b: 39 c2 cmp %eax,%edx ffffffff8106f40d: 74 1b je ffffffff8106f42a <kick_process+0x3a> ffffffff8106f40f: 89 d1 mov %edx,%ecx ffffffff8106f411: 48 c7 c0 00 2c 01 00 mov $0x12c00,%rax ffffffff8106f418: 48 8b 0c cd a0 bc cb mov -0x7e344360(,%rcx,8),%rcx ffffffff8106f41f: 81 ffffffff8106f420: 48 3b bc 08 00 08 00 cmp 0x800(%rax,%rcx,1),%rdi ffffffff8106f427: 00 ffffffff8106f428: 74 1e je ffffffff8106f448 <kick_process+0x58> * ffffffff8106f42a: 65 ff 0c 25 e0 b7 00 decl %gs:0xb7e0 ffffffff8106f431: 00 * ffffffff8106f432: 0f 94 c0 sete %al * ffffffff8106f435: 84 c0 test %al,%al * ffffffff8106f437: 75 02 jne ffffffff8106f43b <kick_process+0x4b> ffffffff8106f439: 5d pop %rbp ffffffff8106f43a: c3 retq * ffffffff8106f43b: e8 b0 b6 f9 ff callq ffffffff8100aaf0 <___preempt_schedule> ffffffff8106f440: 5d pop %rbp ffffffff8106f441: c3 retq ffffffff8106f442: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) ffffffff8106f448: 89 d7 mov %edx,%edi ffffffff8106f44a: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) ffffffff8106f450: ff 15 ea e0 ba 00 callq *0xbae0ea(%rip) # ffffffff81c1d540 <smp_ops+0x20> ffffffff8106f456: eb d2 jmp ffffffff8106f42a <kick_process+0x3a> ffffffff8106f458: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) ffffffff8106f45f: 00 Where the '*' marked lines are preempt_enable(), sadly GCC isn't able to get rid of the sete+test :/ Its a rather frequent pattern in the kernel, so 'fixing' the x86 GCC backend to recognise this might be useful. --- arch/alpha/include/asm/Kbuild | 1 + arch/arc/include/asm/Kbuild | 1 + arch/arm/include/asm/Kbuild | 1 + arch/arm64/include/asm/Kbuild | 1 + arch/avr32/include/asm/Kbuild | 1 + arch/blackfin/include/asm/Kbuild | 1 + arch/c6x/include/asm/Kbuild | 1 + arch/cris/include/asm/Kbuild | 1 + arch/frv/include/asm/Kbuild | 1 + arch/h8300/include/asm/Kbuild | 1 + arch/hexagon/include/asm/Kbuild | 1 + arch/ia64/include/asm/Kbuild | 1 + arch/m32r/include/asm/Kbuild | 1 + arch/m68k/include/asm/Kbuild | 1 + arch/metag/include/asm/Kbuild | 1 + arch/microblaze/include/asm/Kbuild | 1 + arch/mips/include/asm/Kbuild | 1 + arch/mips/mm/init.c | 5 +- arch/mn10300/include/asm/Kbuild | 1 + arch/openrisc/include/asm/Kbuild | 1 + arch/parisc/include/asm/Kbuild | 1 + arch/powerpc/include/asm/Kbuild | 1 + arch/s390/include/asm/Kbuild | 1 + arch/score/include/asm/Kbuild | 1 + arch/sh/include/asm/Kbuild | 1 + arch/sparc/include/asm/Kbuild | 1 + arch/tile/include/asm/Kbuild | 1 + arch/um/include/asm/Kbuild | 1 + arch/unicore32/include/asm/Kbuild | 1 + arch/x86/include/asm/calling.h | 50 +++++++++++++++++ arch/x86/include/asm/thread_info.h | 5 +- arch/x86/kernel/Makefile | 2 + arch/x86/kernel/asm-offsets.c | 1 - arch/x86/kernel/cpu/common.c | 5 ++ arch/x86/kernel/entry_32.S | 7 +-- arch/x86/kernel/entry_64.S | 4 +- arch/x86/kernel/process_32.c | 10 ++++ arch/x86/kernel/process_64.c | 10 ++++ arch/x86/kernel/traps.c | 4 +- arch/xtensa/include/asm/Kbuild | 1 + include/linux/hardirq.h | 8 +-- include/linux/preempt.h | 112 +++++++++++++++++-------------------- include/linux/sched.h | 5 -- include/linux/thread_info.h | 1 + include/linux/uaccess.h | 8 +-- include/trace/events/sched.h | 2 +- init/main.c | 2 +- kernel/context_tracking.c | 4 +- kernel/cpu/idle.c | 7 +++ kernel/sched/core.c | 54 +++++++++--------- kernel/softirq.c | 16 +++--- kernel/timer.c | 8 +-- lib/smp_processor_id.c | 3 +- 53 files changed, 226 insertions(+), 136 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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