The design is for mcount based tracers to be added thru the lib/mcount/tracer_interface.h file, just like mcount users should add themselves to lib/mcount/mcount.h. A Kconfig rule chooses the right MCOUNT and MCOUNT_TRACER user. This is to avoid function call costs for something that is supposed to be used only in a debug kernel and that has to reduce to the bare minimum the per function call overhead of mcount based tracing. Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Steven Rostedt --- lib/mcount/Kconfig | 11 +++ lib/mcount/Makefile | 2 lib/mcount/tracer.c | 125 ++++++++++++++++++++++++++++++++++++++++++ lib/mcount/tracer.h | 21 +++++++ lib/mcount/tracer_interface.h | 14 ++++ 5 files changed, 173 insertions(+) create mode 100644 lib/mcount/tracer.c create mode 100644 lib/mcount/tracer.h create mode 100644 lib/mcount/tracer_interface.h Index: linux-compile.git/lib/mcount/Kconfig =================================================================== --- linux-compile.git.orig/lib/mcount/Kconfig 2008-01-02 23:24:53.000000000 -0500 +++ linux-compile.git/lib/mcount/Kconfig 2008-01-02 23:28:06.000000000 -0500 @@ -4,3 +4,14 @@ config MCOUNT bool depends on DEBUG_KERNEL + +config MCOUNT_TRACER + bool "Profiler instrumentation based tracer" + depends on DEBUG_KERNEL + default n + select MCOUNT + help + Use profiler instrumentation, adding -pg to CFLAGS. This will + insert a call to an architecture specific __mcount routine, + that the debugging mechanism using this facility will hook by + providing a set of inline routines. Index: linux-compile.git/lib/mcount/tracer.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-compile.git/lib/mcount/tracer.c 2008-01-02 23:28:06.000000000 -0500 @@ -0,0 +1,125 @@ +/* + * ring buffer based mcount tracer + * + * Copyright (C) 2007 Arnaldo Carvalho de Melo + * Steven Rostedt + * + * From code in the latency_tracer, that is: + * + * Copyright (C) 2004-2006 Ingo Molnar + * Copyright (C) 2004 William Lee Irwin III + */ + +#include +#include +#include +#include +#include +#include + +#include "tracer.h" +#include "tracer_interface.h" + +static struct mctracer_trace mctracer_trace; + +static inline notrace void +mctracer_add_trace_entry(struct mctracer_trace *tr, + int cpu, + const unsigned long ip, + const unsigned long parent_ip) +{ + unsigned long idx, idx_next; + struct mctracer_entry *entry; + + idx = tr->trace_idx[cpu]; + idx_next = idx + 1; + + if (unlikely(idx_next >= tr->entries)) { + atomic_inc(&tr->underrun[cpu]); + idx_next = 0; + } + + tr->trace_idx[cpu] = idx_next; + + if (unlikely(idx_next != 0 && atomic_read(&tr->underrun[cpu]))) + atomic_inc(&tr->underrun[cpu]); + + entry = tr->trace[cpu] + idx * MCTRACER_ENTRY_SIZE; + entry->idx = atomic_inc_return(&tr->cnt); + entry->ip = ip; + entry->parent_ip = parent_ip; +} + +static inline notrace void trace_function(const unsigned long ip, + const unsigned long parent_ip) +{ + unsigned long flags; + struct mctracer_trace *tr; + int cpu; + + raw_local_irq_save(flags); + cpu = raw_smp_processor_id(); + + tr = &mctracer_trace; + + atomic_inc(&tr->disabled[cpu]); + if (likely(atomic_read(&tr->disabled[cpu]) == 1)) + mctracer_add_trace_entry(tr, cpu, ip, parent_ip); + + atomic_dec(&tr->disabled[cpu]); + + raw_local_irq_restore(flags); +} + + +static inline notrace int page_order(const unsigned long size) +{ + const unsigned long nr_pages = DIV_ROUND_UP(size, PAGE_SIZE); + return ilog2(roundup_pow_of_two(nr_pages)); +} + +static inline notrace int mctracer_alloc_buffers(void) +{ + const int order = page_order(MCTRACER_NR_ENTRIES * MCTRACER_ENTRY_SIZE); + const unsigned long size = (1UL << order) << PAGE_SHIFT; + struct mctracer_entry *array; + int i; + + for_each_possible_cpu(i) { + array = (struct mctracer_entry *) + __get_free_pages(GFP_KERNEL, order); + if (array == NULL) { + printk(KERN_ERR "mctracer: failed to allocate" + " %ld bytes for trace buffer!\n", size); + goto free_buffers; + } + mctracer_trace.trace[i] = array; + } + + /* + * Since we allocate by orders of pages, we may be able to + * round up a bit. + */ + mctracer_trace.entries = size / MCTRACER_ENTRY_SIZE; + + + pr_info("mctracer: %ld bytes allocated for %ld entries of %ld bytes\n", + size, MCTRACER_NR_ENTRIES, MCTRACER_ENTRY_SIZE); + pr_info(" actual entries %ld\n", mctracer_trace.entries); + + register_mcount_function(trace_function); + + return 0; + + free_buffers: + for (i-- ; i >= 0; i--) { + if (mctracer_trace.trace[i]) { + free_pages((unsigned long)mctracer_trace.trace[i], + order); + mctracer_trace.trace[i] = NULL; + } + } + return -ENOMEM; +} + +device_initcall(mctracer_alloc_buffers); Index: linux-compile.git/lib/mcount/tracer.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-compile.git/lib/mcount/tracer.h 2008-01-02 23:28:06.000000000 -0500 @@ -0,0 +1,21 @@ +#ifndef _LINUX_MCOUNT_TRACER_H +#define _LINUX_MCOUNT_TRACER_H + +#include + +struct mctracer_entry { + unsigned long idx; + unsigned long ip; + unsigned long parent_ip; +}; + +struct mctracer_trace { + void *trace[NR_CPUS]; + unsigned long trace_idx[NR_CPUS]; + unsigned long entries; + atomic_t cnt; + atomic_t disabled[NR_CPUS]; + atomic_t underrun[NR_CPUS]; +}; + +#endif /* _LINUX_MCOUNT_TRACER_H */ Index: linux-compile.git/lib/mcount/tracer_interface.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-compile.git/lib/mcount/tracer_interface.h 2008-01-02 23:28:06.000000000 -0500 @@ -0,0 +1,14 @@ +#ifndef _LINUX_MCTRACER_INTERFACE_H +#define _LINUX_MCTRACER_INTERFACE_H + +#include "tracer.h" + +/* + * Will be at least sizeof(struct mctracer_entry), but callers can request more + * space for private stuff, such as a timestamp, preempt_count, etc. + */ +#define MCTRACER_ENTRY_SIZE sizeof(struct mctracer_entry) + +#define MCTRACER_NR_ENTRIES (65536UL) + +#endif /* _LINUX_MCTRACER_INTERFACE_H */ Index: linux-compile.git/lib/mcount/Makefile =================================================================== --- linux-compile.git.orig/lib/mcount/Makefile 2008-01-02 23:24:53.000000000 -0500 +++ linux-compile.git/lib/mcount/Makefile 2008-01-02 23:28:06.000000000 -0500 @@ -1,3 +1,5 @@ obj-$(CONFIG_MCOUNT) += libmcount.o +obj-$(CONFIG_MCOUNT_TRACER) += tracer.o + libmcount-objs := mcount.o -- -- 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/