Shrink overhead of message representation.

benchmark.py

@@ -27,30 +27,33 @@ def GitWorktree(commit):
 def Run(cmd):
   subprocess.check_call(cmd, shell=True)
 
-def Benchmark(outbase, runs=12):
+def Benchmark(outbase, bench_cpu=True, runs=12):
   tmpfile = "/tmp/bench-output.json"
   Run("rm -rf {}".format(tmpfile))
-  Run("bazel test :all")
-  Run("bazel build -c opt :benchmark")
+  Run("CC=clang bazel test :all")
 
-  Run("./bazel-bin/benchmark --benchmark_out_format=json --benchmark_out={} --benchmark_repetitions={}".format(tmpfile, runs))
+  if bench_cpu:
+    Run("CC=clang bazel build -c opt :benchmark")
 
-  Run("bazel build -c opt --copt=-g :conformance_upb")
-  Run("cp -f bazel-bin/conformance_upb {}.bin".format(outbase))
+    Run("./bazel-bin/benchmark --benchmark_out_format=json --benchmark_out={} --benchmark_repetitions={}".format(tmpfile, runs))
+    with open(tmpfile) as f:
+      bench_json = json.load(f)
+
+    # Translate into the format expected by benchstat.
+    with open(outbase + ".txt", "w") as f:
+      for run in bench_json["benchmarks"]:
+        name = re.sub(r'^BM_', 'Benchmark', run["name"])
+        if name.endswith("_mean") or name.endswith("_median") or name.endswith("_stddev"):
+          continue
+        values = (name, run["iterations"], run["cpu_time"])
+        print("{} {} {} ns/op".format(*values), file=f)
 
-  with open(tmpfile) as f:
-    bench_json = json.load(f)
+  Run("CC=clang bazel build -c opt --copt=-g :conformance_upb")
+  Run("cp -f bazel-bin/conformance_upb {}.bin".format(outbase))
 
-  # Translate into the format expected by benchstat.
-  with open(outbase + ".txt", "w") as f:
-    for run in bench_json["benchmarks"]:
-      name = re.sub(r'^BM_', 'Benchmark', run["name"])
-      if name.endswith("_mean") or name.endswith("_median") or name.endswith("_stddev"):
-        continue
-      values = (name, run["iterations"], run["cpu_time"])
-      print("{} {} {} ns/op".format(*values), file=f)
 
 baseline = "master"
+bench_cpu = True
 
 if len(sys.argv) > 1:
   baseline = sys.argv[1]
@@ -60,16 +63,17 @@ if len(sys.argv) > 1:
     pass
 
 # Benchmark our current directory first, since it's more likely to be broken.
-Benchmark("/tmp/new")
+Benchmark("/tmp/new", bench_cpu)
 
 # Benchmark the baseline.
 with GitWorktree(baseline):
-  Benchmark("/tmp/old")
+  Benchmark("/tmp/old", bench_cpu)
 
 print()
 print()
 
-Run("~/go/bin/benchstat /tmp/old.txt /tmp/new.txt")
+if bench_cpu:
+  Run("~/go/bin/benchstat /tmp/old.txt /tmp/new.txt")
 
 print()
 print()

upb/decode.c

@@ -616,7 +616,7 @@ bool upb_decode(const char *buf, size_t size, void *msg, const upb_msglayout *l,
   state.arena.last_size = arena->last_size;
   state.arena.parent = arena;
 
-  if (setjmp(state.err)) {
+  if (UPB_UNLIKELY(setjmp(state.err))) {
     ok = false;
   } else {
     decode_msg(&state, buf, msg, l);

upb/msg.c

@@ -22,73 +22,67 @@ static const char _upb_fieldtype_to_sizelg2[12] = {
   UPB_SIZE(3, 4),  /* UPB_TYPE_BYTES */
 };
 
-static uintptr_t tag_arrptr(void* ptr, int elem_size_lg2) {
-  UPB_ASSERT(elem_size_lg2 <= 4);
-  return (uintptr_t)ptr | elem_size_lg2;
-}
-
-static int upb_msg_internalsize(const upb_msglayout *l) {
-  return sizeof(upb_msg_internal) - l->extendable * sizeof(void *);
-}
-
-static size_t upb_msg_sizeof(const upb_msglayout *l) {
-  return l->size + upb_msg_internalsize(l);
-}
+static const size_t overhead = sizeof(upb_msg_internal);
 
 static const upb_msg_internal *upb_msg_getinternal_const(const upb_msg *msg) {
   ptrdiff_t size = sizeof(upb_msg_internal);
   return UPB_PTR_AT(msg, -size, upb_msg_internal);
 }
 
-static upb_msg_internal *upb_msg_getinternal(upb_msg *msg) {
-  return (upb_msg_internal*)upb_msg_getinternal_const(msg);
+upb_msg *_upb_msg_new(const upb_msglayout *l, upb_arena *a) {
+  return _upb_msg_new_inl(l, a);
 }
 
 void _upb_msg_clear(upb_msg *msg, const upb_msglayout *l) {
-  ptrdiff_t internal = upb_msg_internalsize(l);
-  void *mem = UPB_PTR_AT(msg, -internal, char);
-  memset(mem, 0, l->size + internal);
+  void *mem = UPB_PTR_AT(msg, -sizeof(upb_msg_internal), char);
+  memset(mem, 0, upb_msg_sizeof(l));
 }
 
-upb_msg *_upb_msg_new(const upb_msglayout *l, upb_arena *a) {
-  void *mem = upb_arena_malloc(a, upb_msg_sizeof(l));
-  upb_msg *msg;
-
-  if (!mem) {
-    return NULL;
-  }
-
-  msg = UPB_PTR_AT(mem, upb_msg_internalsize(l), upb_msg);
-  _upb_msg_clear(msg, l);
-  return msg;
+static uintptr_t tag_arrptr(void* ptr, int elem_size_lg2) {
+  UPB_ASSERT(elem_size_lg2 <= 4);
+  return (uintptr_t)ptr | elem_size_lg2;
 }
 
 bool _upb_msg_addunknown(upb_msg *msg, const char *data, size_t len,
                          upb_arena *arena) {
+
   upb_msg_internal *in = upb_msg_getinternal(msg);
-  if (len > in->unknown_size - in->unknown_len) {
-    upb_alloc *alloc = upb_arena_alloc(arena);
-    size_t need = in->unknown_size + len;
-    size_t newsize = UPB_MAX(in->unknown_size * 2, need);
-    void *mem = upb_realloc(alloc, in->unknown, in->unknown_size, newsize);
-    if (!mem) return false;
-    in->unknown = mem;
-    in->unknown_size = newsize;
+  if (!in->unknown) {
+    size_t size = 128;
+    while (size < len) size *= 2;
+    in->unknown = upb_arena_malloc(arena, size + overhead);
+    if (!in->unknown) return false;
+    in->unknown->size = size;
+    in->unknown->len = 0;
+  } else if (in->unknown->size - in->unknown->len < len) {
+    size_t need = in->unknown->len + len;
+    size_t size = in->unknown->size;;
+    while (size < need)  size *= 2;
+    in->unknown = upb_arena_realloc(
+        arena, in->unknown, in->unknown->size + overhead, size + overhead);
+    if (!in->unknown) return false;
   }
-  memcpy(in->unknown + in->unknown_len, data, len);
-  in->unknown_len += len;
+  memcpy(UPB_PTR_AT(in->unknown + 1, in->unknown->len, char), data, len);
+  in->unknown->len += len;
   return true;
 }
 
 void _upb_msg_discardunknown_shallow(upb_msg *msg) {
   upb_msg_internal *in = upb_msg_getinternal(msg);
-  in->unknown_len = 0;
+  if (in->unknown) {
+    in->unknown->len = 0;
+  }
 }
 
 const char *upb_msg_getunknown(const upb_msg *msg, size_t *len) {
   const upb_msg_internal *in = upb_msg_getinternal_const(msg);
-  *len = in->unknown_len;
-  return in->unknown;
+  if (in->unknown) {
+    *len = in->unknown->len;
+    return (char*)(in->unknown + 1);
+  } else {
+    *len = 0;
+    return NULL;
+  }
 }
 
 /** upb_array *****************************************************************/

upb/msg.h

@@ -62,25 +62,41 @@ typedef struct upb_msglayout {
  * compatibility.  We put these before the user's data.  The user's upb_msg*
  * points after the upb_msg_internal. */
 
-/* Used when a message is not extendable. */
 typedef struct {
-  char *unknown;
-  size_t unknown_len;
-  size_t unknown_size;
-} upb_msg_internal;
+  uint32_t len;
+  uint32_t size;
+  /* Data follows. */
+} upb_msg_unknowndata;
 
-/* Used when a message is extendable. */
+/* Used when a message is not extendable. */
 typedef struct {
-  upb_inttable *extdict;
-  upb_msg_internal base;
-} upb_msg_internal_withext;
+  upb_msg_unknowndata *unknown;
+} upb_msg_internal;
 
 /* Maps upb_fieldtype_t -> memory size. */
 extern char _upb_fieldtype_to_size[12];
 
+UPB_INLINE size_t upb_msg_sizeof(const upb_msglayout *l) {
+  return l->size + sizeof(upb_msg_internal);
+}
+
+UPB_INLINE upb_msg *_upb_msg_new_inl(const upb_msglayout *l, upb_arena *a) {
+  size_t size = upb_msg_sizeof(l);
+  void *mem = upb_arena_malloc(a, size);
+  upb_msg *msg;
+  if (UPB_UNLIKELY(!mem)) return NULL;
+  msg = UPB_PTR_AT(mem, sizeof(upb_msg_internal), upb_msg);
+  memset(mem, 0, size);
+  return msg;
+}
+
 /* Creates a new messages with the given layout on the given arena. */
 upb_msg *_upb_msg_new(const upb_msglayout *l, upb_arena *a);
 
+UPB_INLINE upb_msg_internal *upb_msg_getinternal(upb_msg *msg) {
+  return UPB_PTR_AT(msg, -sizeof(upb_msg_internal), upb_msg_internal);
+}
+
 /* Clears the given message. */
 void _upb_msg_clear(upb_msg *msg, const upb_msglayout *l);