Add profiling capability

src/profile.h

@@ -0,0 +1,74 @@
+#pragma once
+#include "iobuf.h"
+
+// Macros to record timestamped events that happens with a connection.
+// They are saved into a c->prof IO buffer, each event is a name and a 32-bit
+// timestamp in milliseconds since connection init time.
+//
+// Test (run in two separate terminals):
+//   make -C examples/http-server/ CFLAGS_EXTRA=-DMG_ENABLE_PROFILE=1
+//   curl localhost:8000
+// Output:
+//   1ea1f1e7 2 net.c:150:mg_close_conn      3 profile:                                                            
+//   1ea1f1e8 2 net.c:150:mg_close_conn      1ea1f1e6 init                                                         
+//   1ea1f1e8 2 net.c:150:mg_close_conn          0 EV_OPEN
+//   1ea1f1e8 2 net.c:150:mg_close_conn          0 EV_ACCEPT 
+//   1ea1f1e8 2 net.c:150:mg_close_conn          0 EV_READ
+//   1ea1f1e8 2 net.c:150:mg_close_conn          0 EV_HTTP_MSG
+//   1ea1f1e8 2 net.c:150:mg_close_conn          0 EV_WRITE
+//   1ea1f1e8 2 net.c:150:mg_close_conn          1 EV_CLOSE
+//
+// Usage:
+//   Enable profiling by setting MG_ENABLE_PROFILE=1
+//   Invoke MG_PROF_ADD(c, "MY_EVENT_1") in the places you'd like to measure
+
+#if MG_ENABLE_PROFILE
+struct mg_profitem {
+  const char *name;    // Event name
+  uint32_t timestamp;  // Milliseconds since connection creation (MG_EV_OPEN)
+};
+
+#define MG_PROFILE_ALLOC_GRANULARITY 256  // Can save 32 items wih to realloc
+
+// Adding a profile item to the c->prof. Must be as fast as possible.
+// Reallocation of the c->prof iobuf is not desirable here, that's why we
+// pre-allocate c->prof with MG_PROFILE_ALLOC_GRANULARITY.
+// This macro just inits and copies 8 bytes, and calls mg_millis(),
+// which should be fast enough.
+#define MG_PROF_ADD(c, name_)                                             \
+  do {                                                                    \
+    struct mg_iobuf *io = &c->prof;                                       \
+    uint32_t inittime = ((struct mg_profitem *) io->buf)->timestamp;      \
+    struct mg_profitem item = {name_, (uint32_t) mg_millis() - inittime}; \
+    mg_iobuf_add(io, io->len, &item, sizeof(item));                       \
+  } while (0)
+
+// Initialising profile for a new connection. Not time sensitive
+#define MG_PROF_INIT(c)                                          \
+  do {                                                           \
+    struct mg_profitem first = {"init", (uint32_t) mg_millis()}; \
+    mg_iobuf_init(&(c)->prof, 0, MG_PROFILE_ALLOC_GRANULARITY);  \
+    mg_iobuf_add(&c->prof, c->prof.len, &first, sizeof(first));  \
+  } while (0)
+
+#define MG_PROF_FREE(c) mg_iobuf_free(&(c)->prof)
+
+// Dumping the profile. Not time sensitive
+#define MG_PROF_DUMP(c)                                            \
+  do {                                                             \
+    struct mg_iobuf *io = &c->prof;                                \
+    struct mg_profitem *p = (struct mg_profitem *) io->buf;        \
+    struct mg_profitem *e = &p[io->len / sizeof(*p)];              \
+    MG_INFO(("%lu profile:", c->id));                              \
+    while (p < e) {                                                \
+      MG_INFO(("%5lx %s", (unsigned long) p->timestamp, p->name)); \
+      p++;                                                         \
+    }                                                              \
+  } while (0)
+
+#else
+#define MG_PROF_INIT(c)
+#define MG_PROF_FREE(c)
+#define MG_PROF_ADD(c, name)
+#define MG_PROF_DUMP(c)
+#endif