perf_counter tools: use mmap() output

update kerneltop to use the mmap() output to gather overflow information

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090323172417.677932499@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 79 insertions, 14 deletions

diff --git a/Documentation/perf_counter/kerneltop.c b/Documentation/perf_counter/kerneltop.c
index a72c9bd28071..80b790553ec8 100644
--- a/Documentation/perf_counter/kerneltop.c
+++ b/Documentation/perf_counter/kerneltop.c
@@ -84,6 +84,7 @@
 #include <sys/prctl.h>
 #include <sys/wait.h>
 #include <sys/uio.h>
+#include <sys/mman.h>
 
 #include <linux/unistd.h>
 
@@ -119,17 +120,25 @@ typedef long long               __s64;
 
 
 #ifdef __x86_64__
-# define __NR_perf_counter_open 295
+#define __NR_perf_counter_open 295
+#define rmb()           asm volatile("lfence" ::: "memory")
+#define cpu_relax()     asm volatile("rep; nop" ::: "memory");
 #endif
 
 #ifdef __i386__
-# define __NR_perf_counter_open 333
+#define __NR_perf_counter_open 333
+#define rmb()           asm volatile("lfence" ::: "memory")
+#define cpu_relax()     asm volatile("rep; nop" ::: "memory");
 #endif
 
 #ifdef __powerpc__
 #define __NR_perf_counter_open 319
+#define rmb()           asm volatile ("sync" ::: "memory")
+#define cpu_relax()     asm volatile ("" ::: "memory");
 #endif
 
+#define unlikely(x)     __builtin_expect(!!(x), 0)
+
 asmlinkage int sys_perf_counter_open(
         struct perf_counter_hw_event    *hw_event_uptr          __user,
         pid_t                           pid,
@@ -181,6 +190,7 @@ static int			profile_cpu			= -1;
 static int                      nr_cpus                         =  0;
 static int                      nmi                             =  1;
 static int                      group                           =  0;
+static unsigned int             page_size;
 
 static char                     *vmlinux;
 
@@ -1117,16 +1127,68 @@ static void process_options(int argc, char *argv[])
         }
 }
 
+struct mmap_data {
+        int counter;
+        void *base;
+        unsigned int mask;
+        unsigned int prev;
+};
+
+static unsigned int mmap_read_head(struct mmap_data *md)
+{
+        struct perf_counter_mmap_page *pc = md->base;
+        unsigned int seq, head;
+
+repeat:
+        rmb();
+        seq = pc->lock;
+
+        if (unlikely(seq & 1)) {
+                cpu_relax();
+                goto repeat;
+        }
+
+        head = pc->data_head;
+
+        rmb();
+        if (pc->lock != seq)
+                goto repeat;
+
+        return head;
+}
+
+static void mmap_read(struct mmap_data *md)
+{
+        unsigned int head = mmap_read_head(md);
+        unsigned int old = md->prev;
+        unsigned char *data = md->base + page_size;
+
+        if (head - old > md->mask) {
+                printf("ERROR: failed to keep up with mmap data\n");
+                exit(-1);
+        }
+
+        for (; old != head;) {
+                __u64 *ptr = (__u64 *)&data[old & md->mask];
+                old += sizeof(__u64);
+
+                process_event(*ptr, md->counter);
+        }
+
+        md->prev = old;
+}
+
 int main(int argc, char *argv[])
 {
         struct pollfd event_array[MAX_NR_CPUS][MAX_COUNTERS];
+        struct mmap_data mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
         struct perf_counter_hw_event hw_event;
         int i, counter, group_fd;
         unsigned int cpu;
-        uint64_t ip;
-        ssize_t res;
         int ret;
 
+        page_size = sysconf(_SC_PAGE_SIZE);
+
         process_options(argc, argv);
 
         nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
@@ -1153,8 +1215,6 @@ int main(int argc, char *argv[])
                         hw_event.record_type    = PERF_RECORD_IRQ;
                         hw_event.nmi            = nmi;
 
-                        printf("FOO: %d %llx %llx\n", counter, event_id[counter], event_count[counter]);
-
                         fd[i][counter] = sys_perf_counter_open(&hw_event, tid, cpu, group_fd, 0);
                         fcntl(fd[i][counter], F_SETFL, O_NONBLOCK);
                         if (fd[i][counter] < 0) {
@@ -1174,6 +1234,17 @@ int main(int argc, char *argv[])
 
                         event_array[i][counter].fd = fd[i][counter];
                         event_array[i][counter].events = POLLIN;
+
+                        mmap_array[i][counter].counter = counter;
+                        mmap_array[i][counter].prev = 0;
+                        mmap_array[i][counter].mask = 2*page_size - 1;
+                        mmap_array[i][counter].base = mmap(NULL, 3*page_size,
+                                        PROT_READ, MAP_SHARED, fd[i][counter], 0);
+                        if (mmap_array[i][counter].base == MAP_FAILED) {
+                                printf("kerneltop error: failed to mmap with %d (%s)\n",
+                                                errno, strerror(errno));
+                                exit(-1);
+                        }
                 }
         }
 
@@ -1188,14 +1259,8 @@ int main(int argc, char *argv[])
                 int hits = events;
 
                 for (i = 0; i < nr_cpus; i++) {
-                        for (counter = 0; counter < nr_counters; counter++) {
-                                res = read(fd[i][counter], (char *) &ip, sizeof(ip));
-                                if (res > 0) {
-                                        assert(res == sizeof(ip));
-
-                                        process_event(ip, counter);
-                                }
-                        }
+                        for (counter = 0; counter < nr_counters; counter++)
+                                mmap_read(&mmap_array[i][counter]);
                 }
 
                 if (time(NULL) >= last_refresh + delay_secs) {