perf jit: Add support for using TSC as a timestamp

[cascardo/linux.git] / tools / perf / jvmti / jvmti_agent.c

diff --git a/tools/perf/jvmti/jvmti_agent.c b/tools/perf/jvmti/jvmti_agent.c
index 6461e02..3573f31 100644 (file)
--- a/tools/perf/jvmti/jvmti_agent.c
+++ b/tools/perf/jvmti/jvmti_agent.c
@@ -92,6 +92,22 @@ error:
        return ret;
 }
 
+static int use_arch_timestamp;
+
+static inline uint64_t
+get_arch_timestamp(void)
+{
+#if defined(__i386__) || defined(__x86_64__)
+       unsigned int low, high;
+
+       asm volatile("rdtsc" : "=a" (low), "=d" (high));
+
+       return low | ((uint64_t)high) << 32;
+#else
+       return 0;
+#endif
+}
+
 #define NSEC_PER_SEC   1000000000
 static int perf_clk_id = CLOCK_MONOTONIC;
 
@@ -107,6 +123,9 @@ perf_get_timestamp(void)
        struct timespec ts;
        int ret;
 
+       if (use_arch_timestamp)
+               return get_arch_timestamp();
+
        ret = clock_gettime(perf_clk_id, &ts);
        if (ret)
                return 0;
@@ -203,6 +222,17 @@ perf_close_marker_file(void)
        munmap(marker_addr, pgsz);
 }
 
+static void
+init_arch_timestamp(void)
+{
+       char *str = getenv("JITDUMP_USE_ARCH_TIMESTAMP");
+
+       if (!str || !*str || !strcmp(str, "0"))
+               return;
+
+       use_arch_timestamp = 1;
+}
+
 void *jvmti_open(void)
 {
        int pad_cnt;
@@ -211,11 +241,17 @@ void *jvmti_open(void)
        int fd;
        FILE *fp;
 
+       init_arch_timestamp();
+
        /*
         * check if clockid is supported
         */
-       if (!perf_get_timestamp())
-               warnx("jvmti: kernel does not support %d clock id", perf_clk_id);
+       if (!perf_get_timestamp()) {
+               if (use_arch_timestamp)
+                       warnx("jvmti: arch timestamp not supported");
+               else
+                       warnx("jvmti: kernel does not support %d clock id", perf_clk_id);
+       }
 
        memset(&header, 0, sizeof(header));
 
@@ -263,6 +299,9 @@ void *jvmti_open(void)
 
        header.timestamp = perf_get_timestamp();
 
+       if (use_arch_timestamp)
+               header.flags |= JITDUMP_FLAGS_ARCH_TIMESTAMP;
+
        if (!fwrite(&header, sizeof(header), 1, fp)) {
                warn("jvmti: cannot write dumpfile header");
                goto error;