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authorJeff Hostetler <jeffhost@microsoft.com>2019-02-22 22:25:01 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-02-22 23:27:59 (GMT)
commitee4512ed481a126dadd33334186e0e759d7f2f47 (patch)
tree4bc0418115d44b1833c1d24d2ac1c92f067b7ad3 /trace2/tr2_tls.c
parente544221d97a57a9be7ba18a0df52a15b4cc76f97 (diff)
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trace2: create new combined trace facility
Create a new unified tracing facility for git. The eventual intent is to replace the current trace_printf* and trace_performance* routines with a unified set of git_trace2* routines. In addition to the usual printf-style API, trace2 provides higer-level event verbs with fixed-fields allowing structured data to be written. This makes post-processing and analysis easier for external tools. Trace2 defines 3 output targets. These are set using the environment variables "GIT_TR2", "GIT_TR2_PERF", and "GIT_TR2_EVENT". These may be set to "1" or to an absolute pathname (just like the current GIT_TRACE). * GIT_TR2 is intended to be a replacement for GIT_TRACE and logs command summary data. * GIT_TR2_PERF is intended as a replacement for GIT_TRACE_PERFORMANCE. It extends the output with columns for the command process, thread, repo, absolute and relative elapsed times. It reports events for child process start/stop, thread start/stop, and per-thread function nesting. * GIT_TR2_EVENT is a new structured format. It writes event data as a series of JSON records. Calls to trace2 functions log to any of the 3 output targets enabled without the need to call different trace_printf* or trace_performance* routines. Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'trace2/tr2_tls.c')
-rw-r--r--trace2/tr2_tls.c164
1 files changed, 164 insertions, 0 deletions
diff --git a/trace2/tr2_tls.c b/trace2/tr2_tls.c
new file mode 100644
index 0000000..8e65b03
--- /dev/null
+++ b/trace2/tr2_tls.c
@@ -0,0 +1,164 @@
+#include "cache.h"
+#include "thread-utils.h"
+#include "trace2/tr2_tls.h"
+
+/*
+ * Initialize size of the thread stack for nested regions.
+ * This is used to store nested region start times. Note that
+ * this stack is per-thread and not per-trace-key.
+ */
+#define TR2_REGION_NESTING_INITIAL_SIZE (100)
+
+static struct tr2tls_thread_ctx *tr2tls_thread_main;
+static uint64_t tr2tls_us_start_main;
+
+static pthread_mutex_t tr2tls_mutex;
+static pthread_key_t tr2tls_key;
+
+static int tr2_next_thread_id; /* modify under lock */
+
+struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name)
+{
+ uint64_t us_now = getnanotime() / 1000;
+ struct tr2tls_thread_ctx *ctx = xcalloc(1, sizeof(*ctx));
+
+ /*
+ * Implicitly "tr2tls_push_self()" to capture the thread's start
+ * time in array_us_start[0]. For the main thread this gives us the
+ * application run time.
+ */
+ ctx->alloc = TR2_REGION_NESTING_INITIAL_SIZE;
+ ctx->array_us_start = (uint64_t *)xcalloc(ctx->alloc, sizeof(uint64_t));
+ ctx->array_us_start[ctx->nr_open_regions++] = us_now;
+
+ ctx->thread_id = tr2tls_locked_increment(&tr2_next_thread_id);
+
+ strbuf_init(&ctx->thread_name, 0);
+ if (ctx->thread_id)
+ strbuf_addf(&ctx->thread_name, "th%02d:", ctx->thread_id);
+ strbuf_addstr(&ctx->thread_name, thread_name);
+ if (ctx->thread_name.len > TR2_MAX_THREAD_NAME)
+ strbuf_setlen(&ctx->thread_name, TR2_MAX_THREAD_NAME);
+
+ pthread_setspecific(tr2tls_key, ctx);
+
+ return ctx;
+}
+
+struct tr2tls_thread_ctx *tr2tls_get_self(void)
+{
+ struct tr2tls_thread_ctx *ctx = pthread_getspecific(tr2tls_key);
+
+ /*
+ * If the thread-proc did not call trace2_thread_start(), we won't
+ * have any TLS data associated with the current thread. Fix it
+ * here and silently continue.
+ */
+ if (!ctx)
+ ctx = tr2tls_create_self("unknown");
+
+ return ctx;
+}
+
+int tr2tls_is_main_thread(void)
+{
+ struct tr2tls_thread_ctx *ctx = pthread_getspecific(tr2tls_key);
+
+ return ctx == tr2tls_thread_main;
+}
+
+void tr2tls_unset_self(void)
+{
+ struct tr2tls_thread_ctx *ctx;
+
+ ctx = tr2tls_get_self();
+
+ pthread_setspecific(tr2tls_key, NULL);
+
+ free(ctx->array_us_start);
+ free(ctx);
+}
+
+void tr2tls_push_self(uint64_t us_now)
+{
+ struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
+
+ ALLOC_GROW(ctx->array_us_start, ctx->nr_open_regions + 1, ctx->alloc);
+ ctx->array_us_start[ctx->nr_open_regions++] = us_now;
+}
+
+void tr2tls_pop_self(void)
+{
+ struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
+
+ if (!ctx->nr_open_regions)
+ BUG("no open regions in thread '%s'", ctx->thread_name.buf);
+
+ ctx->nr_open_regions--;
+}
+
+void tr2tls_pop_unwind_self(void)
+{
+ struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
+
+ while (ctx->nr_open_regions > 1)
+ tr2tls_pop_self();
+}
+
+uint64_t tr2tls_region_elasped_self(uint64_t us)
+{
+ struct tr2tls_thread_ctx *ctx;
+ uint64_t us_start;
+
+ ctx = tr2tls_get_self();
+ if (!ctx->nr_open_regions)
+ return 0;
+
+ us_start = ctx->array_us_start[ctx->nr_open_regions - 1];
+
+ return us - us_start;
+}
+
+uint64_t tr2tls_absolute_elapsed(uint64_t us)
+{
+ if (!tr2tls_thread_main)
+ return 0;
+
+ return us - tr2tls_us_start_main;
+}
+
+void tr2tls_init(void)
+{
+ pthread_key_create(&tr2tls_key, NULL);
+ init_recursive_mutex(&tr2tls_mutex);
+
+ tr2tls_thread_main = tr2tls_create_self("main");
+ /*
+ * Keep a copy of the absolute start time of the main thread
+ * in a fixed variable since other threads need to access it.
+ * This also eliminates the need to lock accesses to the main
+ * thread's array (because of reallocs).
+ */
+ tr2tls_us_start_main = tr2tls_thread_main->array_us_start[0];
+}
+
+void tr2tls_release(void)
+{
+ tr2tls_unset_self();
+ tr2tls_thread_main = NULL;
+
+ pthread_mutex_destroy(&tr2tls_mutex);
+ pthread_key_delete(tr2tls_key);
+}
+
+int tr2tls_locked_increment(int *p)
+{
+ int current_value;
+
+ pthread_mutex_lock(&tr2tls_mutex);
+ current_value = *p;
+ *p = current_value + 1;
+ pthread_mutex_unlock(&tr2tls_mutex);
+
+ return current_value;
+}