From c08c820508233b424deab3302bc404bbecc6493a Mon Sep 17 00:00:00 2001 From: Vojtech Pavlik Date: Tue, 26 Sep 2006 10:52:28 +0200 Subject: [PATCH] [PATCH] Add the vgetcpu vsyscall This patch adds a vgetcpu vsyscall, which depending on the CPU RDTSCP capability uses either the RDTSCP or CPUID to obtain a CPU and node numbers and pass them to the program. AK: Lots of changes over Vojtech's original code: Better prototype for vgetcpu() It's better to pass the cpu / node numbers as separate arguments to avoid mistakes when going from SMP to NUMA. Also add a fast time stamp based cache using a user supplied argument to speed things more up. Use fast method from Chuck Ebbert to retrieve node/cpu from GDT limit instead of CPUID Made sure RDTSCP init is always executed after node is known. Drop printk Signed-off-by: Vojtech Pavlik Signed-off-by: Andi Kleen --- arch/x86_64/kernel/head.S | 2 +- arch/x86_64/kernel/time.c | 13 ++--- arch/x86_64/kernel/vmlinux.lds.S | 3 ++ arch/x86_64/kernel/vsyscall.c | 84 +++++++++++++++++++++++++++++++- include/asm-x86_64/segment.h | 5 +- include/asm-x86_64/smp.h | 12 +++-- include/asm-x86_64/vsyscall.h | 9 ++++ include/linux/getcpu.h | 16 ++++++ 8 files changed, 130 insertions(+), 14 deletions(-) create mode 100644 include/linux/getcpu.h diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S index c9739ca81d06..505ec4a57506 100644 --- a/arch/x86_64/kernel/head.S +++ b/arch/x86_64/kernel/head.S @@ -371,7 +371,7 @@ ENTRY(cpu_gdt_table) .quad 0,0 /* TSS */ .quad 0,0 /* LDT */ .quad 0,0,0 /* three TLS descriptors */ - .quad 0 /* unused */ + .quad 0x0000f40000000000 /* node/CPU stored in limit */ gdt_end: /* asm/segment.h:GDT_ENTRIES must match this */ /* This should be a multiple of the cache line size */ diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 97b9e46d1992..560ed944dc0e 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -899,12 +899,8 @@ static int __cpuinit time_cpu_notifier(struct notifier_block *nb, unsigned long action, void *hcpu) { unsigned cpu = (unsigned long) hcpu; - if (action == CPU_ONLINE && - cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP)) { - unsigned p; - p = smp_processor_id() | (cpu_to_node(smp_processor_id())<<12); - write_rdtscp_aux(p); - } + if (action == CPU_ONLINE) + vsyscall_set_cpu(cpu); return NOTIFY_DONE; } @@ -993,6 +989,11 @@ void time_init_gtod(void) if (unsynchronized_tsc()) notsc = 1; + if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP)) + vgetcpu_mode = VGETCPU_RDTSCP; + else + vgetcpu_mode = VGETCPU_LSL; + if (vxtime.hpet_address && notsc) { timetype = hpet_use_timer ? "HPET" : "PIT/HPET"; if (hpet_use_timer) diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S index 7c4de31471d4..8d5a5149bb3a 100644 --- a/arch/x86_64/kernel/vmlinux.lds.S +++ b/arch/x86_64/kernel/vmlinux.lds.S @@ -99,6 +99,9 @@ SECTIONS .vxtime : AT(VLOAD(.vxtime)) { *(.vxtime) } vxtime = VVIRT(.vxtime); + .vgetcpu_mode : AT(VLOAD(.vgetcpu_mode)) { *(.vgetcpu_mode) } + vgetcpu_mode = VVIRT(.vgetcpu_mode); + .wall_jiffies : AT(VLOAD(.wall_jiffies)) { *(.wall_jiffies) } wall_jiffies = VVIRT(.wall_jiffies); diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c index f603037df162..902783bc4d53 100644 --- a/arch/x86_64/kernel/vsyscall.c +++ b/arch/x86_64/kernel/vsyscall.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #include @@ -33,11 +34,15 @@ #include #include #include +#include +#include +#include #define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr))) int __sysctl_vsyscall __section_sysctl_vsyscall = 1; seqlock_t __xtime_lock __section_xtime_lock = SEQLOCK_UNLOCKED; +int __vgetcpu_mode __section_vgetcpu_mode; #include @@ -127,9 +132,46 @@ time_t __vsyscall(1) vtime(time_t *t) return __xtime.tv_sec; } -long __vsyscall(2) venosys_0(void) +/* Fast way to get current CPU and node. + This helps to do per node and per CPU caches in user space. + The result is not guaranteed without CPU affinity, but usually + works out because the scheduler tries to keep a thread on the same + CPU. + + tcache must point to a two element sized long array. + All arguments can be NULL. */ +long __vsyscall(2) +vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache) { - return -ENOSYS; + unsigned int dummy, p; + unsigned long j = 0; + + /* Fast cache - only recompute value once per jiffies and avoid + relatively costly rdtscp/cpuid otherwise. + This works because the scheduler usually keeps the process + on the same CPU and this syscall doesn't guarantee its + results anyways. + We do this here because otherwise user space would do it on + its own in a likely inferior way (no access to jiffies). + If you don't like it pass NULL. */ + if (tcache && tcache->t0 == (j = __jiffies)) { + p = tcache->t1; + } else if (__vgetcpu_mode == VGETCPU_RDTSCP) { + /* Load per CPU data from RDTSCP */ + rdtscp(dummy, dummy, p); + } else { + /* Load per CPU data from GDT */ + asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); + } + if (tcache) { + tcache->t0 = j; + tcache->t1 = p; + } + if (cpu) + *cpu = p & 0xfff; + if (node) + *node = p >> 12; + return 0; } long __vsyscall(3) venosys_1(void) @@ -200,6 +242,43 @@ static ctl_table kernel_root_table2[] = { #endif +static void __cpuinit write_rdtscp_cb(void *info) +{ + write_rdtscp_aux((unsigned long)info); +} + +void __cpuinit vsyscall_set_cpu(int cpu) +{ + unsigned long *d; + unsigned long node = 0; +#ifdef CONFIG_NUMA + node = cpu_to_node[cpu]; +#endif + if (cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP)) { + void *info = (void *)((node << 12) | cpu); + /* Can happen on preemptive kernel */ + if (get_cpu() == cpu) + write_rdtscp_cb(info); +#ifdef CONFIG_SMP + else { + /* the notifier is unfortunately not executed on the + target CPU */ + smp_call_function_single(cpu,write_rdtscp_cb,info,0,1); + } +#endif + put_cpu(); + } + + /* Store cpu number in limit so that it can be loaded quickly + in user space in vgetcpu. + 12 bits for the CPU and 8 bits for the node. */ + d = (unsigned long *)(cpu_gdt(cpu) + GDT_ENTRY_PER_CPU); + *d = 0x0f40000000000ULL; + *d |= cpu; + *d |= (node & 0xf) << 12; + *d |= (node >> 4) << 48; +} + static void __init map_vsyscall(void) { extern char __vsyscall_0; @@ -214,6 +293,7 @@ static int __init vsyscall_init(void) VSYSCALL_ADDR(__NR_vgettimeofday))); BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime)); BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE))); + BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu)); map_vsyscall(); #ifdef CONFIG_SYSCTL register_sysctl_table(kernel_root_table2, 0); diff --git a/include/asm-x86_64/segment.h b/include/asm-x86_64/segment.h index d4bed33fb32c..334ddcdd8f92 100644 --- a/include/asm-x86_64/segment.h +++ b/include/asm-x86_64/segment.h @@ -20,15 +20,16 @@ #define __USER_CS 0x33 /* 6*8+3 */ #define __USER32_DS __USER_DS -#define GDT_ENTRY_TLS 1 #define GDT_ENTRY_TSS 8 /* needs two entries */ #define GDT_ENTRY_LDT 10 /* needs two entries */ #define GDT_ENTRY_TLS_MIN 12 #define GDT_ENTRY_TLS_MAX 14 -/* 15 free */ #define GDT_ENTRY_TLS_ENTRIES 3 +#define GDT_ENTRY_PER_CPU 15 /* Abused to load per CPU data from limit */ +#define __PER_CPU_SEG (GDT_ENTRY_PER_CPU * 8 + 3) + /* TLS indexes for 64bit - hardcoded in arch_prctl */ #define FS_TLS 0 #define GS_TLS 1 diff --git a/include/asm-x86_64/smp.h b/include/asm-x86_64/smp.h index 6805e1feb300..d61547fd833b 100644 --- a/include/asm-x86_64/smp.h +++ b/include/asm-x86_64/smp.h @@ -133,13 +133,19 @@ static __inline int logical_smp_processor_id(void) /* we don't want to mark this access volatile - bad code generation */ return GET_APIC_LOGICAL_ID(*(unsigned long *)(APIC_BASE+APIC_LDR)); } -#endif #ifdef CONFIG_SMP #define cpu_physical_id(cpu) x86_cpu_to_apicid[cpu] #else #define cpu_physical_id(cpu) boot_cpu_id -#endif - +static inline int smp_call_function_single(int cpuid, void (*func) (void *info), + void *info, int retry, int wait) +{ + /* Disable interrupts here? */ + func(info); + return 0; +} +#endif /* !CONFIG_SMP */ +#endif /* !__ASSEMBLY */ #endif diff --git a/include/asm-x86_64/vsyscall.h b/include/asm-x86_64/vsyscall.h index 146b24402a5f..2281e9399b96 100644 --- a/include/asm-x86_64/vsyscall.h +++ b/include/asm-x86_64/vsyscall.h @@ -4,6 +4,7 @@ enum vsyscall_num { __NR_vgettimeofday, __NR_vtime, + __NR_vgetcpu, }; #define VSYSCALL_START (-10UL << 20) @@ -15,6 +16,7 @@ enum vsyscall_num { #include #define __section_vxtime __attribute__ ((unused, __section__ (".vxtime"), aligned(16))) +#define __section_vgetcpu_mode __attribute__ ((unused, __section__ (".vgetcpu_mode"), aligned(16))) #define __section_wall_jiffies __attribute__ ((unused, __section__ (".wall_jiffies"), aligned(16))) #define __section_jiffies __attribute__ ((unused, __section__ (".jiffies"), aligned(16))) #define __section_sys_tz __attribute__ ((unused, __section__ (".sys_tz"), aligned(16))) @@ -26,6 +28,9 @@ enum vsyscall_num { #define VXTIME_HPET 2 #define VXTIME_PMTMR 3 +#define VGETCPU_RDTSCP 1 +#define VGETCPU_LSL 2 + struct vxtime_data { long hpet_address; /* HPET base address */ int last; @@ -40,6 +45,7 @@ struct vxtime_data { /* vsyscall space (readonly) */ extern struct vxtime_data __vxtime; +extern int __vgetcpu_mode; extern struct timespec __xtime; extern volatile unsigned long __jiffies; extern unsigned long __wall_jiffies; @@ -48,6 +54,7 @@ extern seqlock_t __xtime_lock; /* kernel space (writeable) */ extern struct vxtime_data vxtime; +extern int vgetcpu_mode; extern unsigned long wall_jiffies; extern struct timezone sys_tz; extern int sysctl_vsyscall; @@ -55,6 +62,8 @@ extern seqlock_t xtime_lock; extern int sysctl_vsyscall; +extern void vsyscall_set_cpu(int cpu); + #define ARCH_HAVE_XTIME_LOCK 1 #endif /* __KERNEL__ */ diff --git a/include/linux/getcpu.h b/include/linux/getcpu.h new file mode 100644 index 000000000000..031ed3780e45 --- /dev/null +++ b/include/linux/getcpu.h @@ -0,0 +1,16 @@ +#ifndef _LINUX_GETCPU_H +#define _LINUX_GETCPU_H 1 + +/* Cache for getcpu() to speed it up. Results might be upto a jiffie + out of date, but will be faster. + User programs should not refer to the contents of this structure. + It is only a cache for vgetcpu(). It might change in future kernels. + The user program must store this information per thread (__thread) + If you want 100% accurate information pass NULL instead. */ +struct getcpu_cache { + unsigned long t0; + unsigned long t1; + unsigned long res[4]; +}; + +#endif -- 2.20.1