In message <20030522104944.GE27614@in.ibm.com> you write:
> On Thu, May 22, 2003 at 06:36:31PM +1000, Rusty Russell wrote:
> > If you're interested I can probably produce such a patch for x86...
>
> Sure, it might help per-cpu data but will it cause performance
> regression elsewhere? (other users of smp_processor_id). I can run it
> through the same tests and find out. Maybe it'll make good paper material
> for later? ;)
OK, here's an x86-specific patch. It boots for me. I'm mainly
interested in the question of whether it increases static percpu
speed.
Thanks!
Rusty.
-- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.Name: Put __per_cpu_offset in the thread struct, remove cpu Author: Rusty Russell Status: Tested on 2.5.69-bk15, dual x86
D: If we had an efficient kmalloc_percpu-equiv, and moved more structures D: across to it (or to DECLARE_PER_CPU), it makes more sense to derive D: smp_processor_id() from the per-cpu offset, rather than the other way D: around. D: D: This patch is an x86-only hack to do just that, for benchmarking. D: It introduces a new header, asm/task_cpu.h, because I couldn't D: resolve the horrible header tangle any other way.
diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/arch/i386/kernel/i386_ksyms.c working-2.5.69-bk15-offset-uber-alles/arch/i386/kernel/i386_ksyms.c --- linux-2.5.69-bk15/arch/i386/kernel/i386_ksyms.c 2003-05-22 10:48:33.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/arch/i386/kernel/i386_ksyms.c 2003-05-23 16:13:53.000000000 +1000 @@ -152,6 +152,7 @@ EXPORT_SYMBOL(cpu_online_map); EXPORT_SYMBOL(cpu_callout_map); EXPORT_SYMBOL_NOVERS(__write_lock_failed); EXPORT_SYMBOL_NOVERS(__read_lock_failed); +EXPORT_PER_CPU_SYMBOL(__processor_id); /* Global SMP stuff */ EXPORT_SYMBOL(synchronize_irq); diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/arch/i386/kernel/smpboot.c working-2.5.69-bk15-offset-uber-alles/arch/i386/kernel/smpboot.c --- linux-2.5.69-bk15/arch/i386/kernel/smpboot.c 2003-05-22 10:48:33.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/arch/i386/kernel/smpboot.c 2003-05-23 16:12:27.000000000 +1000 @@ -49,6 +49,7 @@ #include <asm/tlbflush.h> #include <asm/desc.h> #include <asm/arch_hooks.h> +#include <asm/task_cpu.h> #include <mach_apic.h> #include <mach_wakecpu.h> @@ -947,7 +948,6 @@ static void __init smp_boot_cpus(unsigne boot_cpu_logical_apicid = logical_smp_processor_id(); - current_thread_info()->cpu = 0; smp_tune_scheduling(); /* @@ -1129,6 +1130,38 @@ void __devinit smp_prepare_boot_cpu(void set_bit(smp_processor_id(), &cpu_callout_map); } +DEFINE_PER_CPU(u32, __processor_id); +unsigned long __per_cpu_offset[NR_CPUS]; + +void __init setup_per_cpu_areas(void) +{ + unsigned long size, i; + char *ptr; + /* Created by linker magic */ + extern char __per_cpu_start[], __per_cpu_end[]; + + /* Copy section for each CPU (we discard the original) */ + size = ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES); + if (!size) + return; + + ptr = alloc_bootmem(size * NR_CPUS); + + for (i = 0; i < NR_CPUS; i++, ptr += size) { + __per_cpu_offset[i] = ptr - __per_cpu_start; + memcpy(ptr, __per_cpu_start, size); + } + + /* Now, setup per-cpu stuff so smp_processor_id() will work when + * we boot other CPUs */ + for (i = 0; i < NR_CPUS; i++) + per_cpu(__processor_id, i) = i; + + /* Our pcpuoff points into the original .data.percpu section: + that will vanish, so fixup now. */ + set_task_cpu(current, smp_processor_id()); +} + int __devinit __cpu_up(unsigned int cpu) { /* This only works at boot for x86. See "rewrite" above. */ diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/fs/proc/array.c working-2.5.69-bk15-offset-uber-alles/fs/proc/array.c --- linux-2.5.69-bk15/fs/proc/array.c 2003-05-05 12:37:09.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/fs/proc/array.c 2003-05-23 16:00:42.000000000 +1000 @@ -78,6 +78,7 @@ #include <asm/pgtable.h> #include <asm/io.h> #include <asm/processor.h> +#include <asm/task_cpu.h> /* Gcc optimizes away "strlen(x)" for constant x */ #define ADDBUF(buffer, string) \ diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/include/asm-i386/percpu.h working-2.5.69-bk15-offset-uber-alles/include/asm-i386/percpu.h --- linux-2.5.69-bk15/include/asm-i386/percpu.h 2003-01-02 12:00:21.000000000 +1100 +++ working-2.5.69-bk15-offset-uber-alles/include/asm-i386/percpu.h 2003-05-23 16:05:22.000000000 +1000 @@ -1,6 +1,40 @@ #ifndef __ARCH_I386_PERCPU__ #define __ARCH_I386_PERCPU__ -#include <asm-generic/percpu.h> +#include <linux/compiler.h> + +#ifdef CONFIG_SMP + +extern void setup_per_cpu_areas(void); +extern unsigned long __per_cpu_offset[NR_CPUS]; + +/* Separate out the type, so (int[3], foo) works. */ +#ifndef MODULE +#define DEFINE_PER_CPU(type, name) \ + __attribute__((__section__(".data.percpu"))) __typeof__(type) name##__per_cpu +#endif + +/* var is in discarded region: offset to particular copy we want */ +#define per_cpu(var, cpu) (*RELOC_HIDE(&var##__per_cpu, __per_cpu_offset[cpu])) +#define __get_cpu_var(var) \ + (*RELOC_HIDE(&var##__per_cpu, current_thread_info()->pcpuoff)) + +#else /* ! SMP */ + +/* Can't define per-cpu variables in modules. Sorry --RR */ +#ifndef MODULE +#define DEFINE_PER_CPU(type, name) \ + __typeof__(type) name##__per_cpu +#endif + +#define per_cpu(var, cpu) ((void)cpu, var##__per_cpu) +#define __get_cpu_var(var) var##__per_cpu + +#endif /* SMP */ + +#define DECLARE_PER_CPU(type, name) extern __typeof__(type) name##__per_cpu + +#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var##__per_cpu) +#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var##__per_cpu) #endif /* __ARCH_I386_PERCPU__ */ diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/include/asm-i386/smp.h working-2.5.69-bk15-offset-uber-alles/include/asm-i386/smp.h --- linux-2.5.69-bk15/include/asm-i386/smp.h 2003-05-22 10:49:07.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/include/asm-i386/smp.h 2003-05-23 16:02:53.000000000 +1000 @@ -8,6 +8,7 @@ #include <linux/config.h> #include <linux/kernel.h> #include <linux/threads.h> +#include <asm/percpu.h> #endif #ifdef CONFIG_X86_LOCAL_APIC @@ -53,7 +54,8 @@ extern void zap_low_mappings (void); * from the initial startup. We map APIC_BASE very early in page_setup(), * so this is correct in the x86 case. */ -#define smp_processor_id() (current_thread_info()->cpu) +DECLARE_PER_CPU(u32, __processor_id); +#define smp_processor_id() __get_cpu_var(__processor_id) extern volatile unsigned long cpu_callout_map; diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/include/asm-i386/task_cpu.h working-2.5.69-bk15-offset-uber-alles/include/asm-i386/task_cpu.h --- linux-2.5.69-bk15/include/asm-i386/task_cpu.h 1970-01-01 10:00:00.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/include/asm-i386/task_cpu.h 2003-05-23 16:02:41.000000000 +1000 @@ -0,0 +1,17 @@ +#ifndef _ASM_I386_TASK_CPU_H +#define _ASM_I386_TASK_CPU_H +#include <linux/percpu.h> +#include <linux/sched.h> + +static inline unsigned int task_cpu(struct task_struct *p) +{ + return (*RELOC_HIDE(&__processor_id__per_cpu, + p->thread_info->pcpuoff)); +} + +static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) +{ + /* CPU is derived. We need to set the per-cpu offset. */ + p->thread_info->pcpuoff = __per_cpu_offset[cpu]; +} +#endif diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/include/asm-i386/thread_info.h working-2.5.69-bk15-offset-uber-alles/include/asm-i386/thread_info.h --- linux-2.5.69-bk15/include/asm-i386/thread_info.h 2003-03-18 12:21:39.000000000 +1100 +++ working-2.5.69-bk15-offset-uber-alles/include/asm-i386/thread_info.h 2003-05-23 15:54:14.000000000 +1000 @@ -26,7 +26,7 @@ struct thread_info { struct exec_domain *exec_domain; /* execution domain */ unsigned long flags; /* low level flags */ unsigned long status; /* thread-synchronous flags */ - __u32 cpu; /* current CPU */ + unsigned long pcpuoff; /* per-cpu offset */ __s32 preempt_count; /* 0 => preemptable, <0 => BUG */ mm_segment_t addr_limit; /* thread address space: @@ -45,7 +45,7 @@ struct thread_info { #define TI_EXEC_DOMAIN 0x00000004 #define TI_FLAGS 0x00000008 #define TI_STATUS 0x0000000C -#define TI_CPU 0x00000010 +#define TI_PCPUOFF 0x00000010 #define TI_PRE_COUNT 0x00000014 #define TI_ADDR_LIMIT 0x00000018 #define TI_RESTART_BLOCK 0x000001C @@ -66,7 +66,7 @@ struct thread_info { .task = &tsk, \ .exec_domain = &default_exec_domain, \ .flags = 0, \ - .cpu = 0, \ + .pcpuoff = 0, \ .preempt_count = 1, \ .addr_limit = KERNEL_DS, \ .restart_block = { \ diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/include/linux/sched.h working-2.5.69-bk15-offset-uber-alles/include/linux/sched.h --- linux-2.5.69-bk15/include/linux/sched.h 2003-05-22 10:49:18.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/include/linux/sched.h 2003-05-23 15:38:53.000000000 +1000 @@ -813,20 +813,7 @@ extern void signal_wake_up(struct task_s /* * Wrappers for p->thread_info->cpu access. No-op on UP. */ -#ifdef CONFIG_SMP - -static inline unsigned int task_cpu(struct task_struct *p) -{ - return p->thread_info->cpu; -} - -static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) -{ - p->thread_info->cpu = cpu; -} - -#else - +#ifndef CONFIG_SMP static inline unsigned int task_cpu(struct task_struct *p) { return 0; diff -urNp --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.69-bk15/kernel/sched.c working-2.5.69-bk15-offset-uber-alles/kernel/sched.c --- linux-2.5.69-bk15/kernel/sched.c 2003-05-22 10:49:22.000000000 +1000 +++ working-2.5.69-bk15-offset-uber-alles/kernel/sched.c 2003-05-23 16:03:55.000000000 +1000 @@ -32,6 +32,7 @@ #include <linux/delay.h> #include <linux/timer.h> #include <linux/rcupdate.h> +#include <asm/task_cpu.h> #ifdef CONFIG_NUMA #define cpu_to_node_mask(cpu) node_to_cpumask(cpu_to_node(cpu)) @@ -1312,7 +1313,7 @@ pick_next_task: switch_tasks: prefetch(next); clear_tsk_need_resched(prev); - RCU_qsctr(prev->thread_info->cpu)++; + RCU_qsctr(task_cpu(prev))++; if (likely(prev != next)) { rq->nr_switches++; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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