4:24 p.m.
For GCC only, define unlikely() macro. Use it on error paths to move
code out of the hot path.
In the server only, use the debug() macro (don't call nbdkit_debug
directly). This macro checks the verbose flag and moves the call to
nbdkit_debug out of the hot path.
---
server/connections.c | 11 ++++++-----
server/internal.h | 17 ++++++++++++++++-
server/plugins.c | 2 +-
server/protocol.c | 4 ++--
server/sockets.c | 4 ++--
5 files changed, 27 insertions(+), 11 deletions(-)
diff --git a/server/connections.c b/server/connections.c
index c55d381..95d8296 100644
--- a/server/connections.c
+++ b/server/connections.c
@@ -97,7 +97,7 @@ connection_set_status (struct connection *conn, int value)
assert (conn->status_pipe[1] >= 0);
if (write (conn->status_pipe[1], &c, 1) != 1 && errno != EAGAIN)
- nbdkit_debug ("failed to notify pipe-to-self: %m");
+ debug ("failed to notify pipe-to-self: %m");
}
conn->status = value;
}
@@ -176,7 +176,7 @@ _handle_single_connection (int sockin, int sockout)
debug ("handshake complete, processing requests with %d threads",
nworkers);
workers = calloc (nworkers, sizeof *workers);
- if (!workers) {
+ if (unlikely (!workers)) {
perror ("malloc");
goto done;
}
@@ -185,12 +185,13 @@ _handle_single_connection (int sockin, int sockout)
struct worker_data *worker = malloc (sizeof *worker);
int err;
- if (!worker) {
+ if (unlikely (!worker)) {
perror ("malloc");
connection_set_status (conn, -1);
goto wait;
}
- if (asprintf (&worker->name, "%s.%d", plugin_name, nworkers) <
0) {
+ if (unlikely (asprintf (&worker->name, "%s.%d", plugin_name,
nworkers)
+ < 0)) {
perror ("asprintf");
connection_set_status (conn, -1);
free (worker);
@@ -199,7 +200,7 @@ _handle_single_connection (int sockin, int sockout)
worker->conn = conn;
err = pthread_create (&workers[nworkers], NULL, connection_worker,
worker);
- if (err) {
+ if (unlikely (err)) {
errno = err;
perror ("pthread_create");
connection_set_status (conn, -1);
diff --git a/server/internal.h b/server/internal.h
index 5e11e1a..7e0c375 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -45,6 +45,17 @@
#include "cleanup.h"
#include "nbd-protocol.h"
+/* Define unlikely macro, but only for GCC. These are used to move
+ * debug and error handling code out of hot paths.
+ */
+#if defined(__GNUC__)
+#define unlikely(x) __builtin_expect (!!(x), 0)
+#define if_verbose if (unlikely (verbose))
+#else
+#define unlikely(x) (x)
+#define if_verbose if (verbose)
+#endif
+
#ifdef __APPLE__
#define UNIX_PATH_MAX 104
#else
@@ -262,7 +273,11 @@ extern int crypto_negotiate_tls (struct connection *conn,
__attribute__((__nonnull__ (1)));
/* debug.c */
-#define debug nbdkit_debug
+#define debug(fs, ...) \
+ do { \
+ if_verbose \
+ nbdkit_debug ((fs), ##__VA_ARGS__); \
+ } while (0)
/* log-*.c */
#if !HAVE_VFPRINTF_PERCENT_M
diff --git a/server/plugins.c b/server/plugins.c
index 87daaf2..65f6817 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -71,7 +71,7 @@ plugin_thread_model (struct backend *b)
#if !(defined SOCK_CLOEXEC && defined HAVE_MKOSTEMP && defined HAVE_PIPE2
&& \
defined HAVE_ACCEPT4)
if (thread_model > NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
- nbdkit_debug ("system lacks atomic CLOEXEC, serializing to avoid fd
leaks");
+ debug ("system lacks atomic CLOEXEC, serializing to avoid fd leaks");
thread_model = NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS;
}
#endif
diff --git a/server/protocol.c b/server/protocol.c
index 89fbdfa..f6ea35c 100644
--- a/server/protocol.c
+++ b/server/protocol.c
@@ -508,8 +508,8 @@ extents_to_block_descriptors (struct nbdkit_extents *extents,
#if 0
for (i = 0; i < *nr_blocks; ++i)
- nbdkit_debug ("block status: sending block %" PRIu32 " type %"
PRIu32,
- blocks[i].length, blocks[i].status_flags);
+ debug ("block status: sending block %" PRIu32 " type %" PRIu32,
+ blocks[i].length, blocks[i].status_flags);
#endif
/* Convert to big endian for the protocol. */
diff --git a/server/sockets.c b/server/sockets.c
index 1585a09..119cb99 100644
--- a/server/sockets.c
+++ b/server/sockets.c
@@ -365,7 +365,7 @@ accept_connection (int listen_sock)
const int flag = 1;
thread_data = malloc (sizeof *thread_data);
- if (!thread_data) {
+ if (unlikely (!thread_data)) {
perror ("malloc");
return;
}
@@ -409,7 +409,7 @@ accept_connection (int listen_sock)
pthread_attr_setdetachstate (&attrs, PTHREAD_CREATE_DETACHED);
err = pthread_create (&thread, &attrs, start_thread, thread_data);
pthread_attr_destroy (&attrs);
- if (err != 0) {
+ if (unlikely (err != 0)) {
fprintf (stderr, "%s: pthread_create: %s\n", program_name, strerror
(err));
close (thread_data->sock);
free (thread_data);
--
2.23.0