syslogd: stop doing open/fstat/lseek/close on _every_ write

(still doing it if more than a second passed in between).
Costs ~40 bytes.

diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index f4644f218d902c69a72cc8c096fa8178ddc441fc..7edce7a0ae347cfda5eaa037f1c58aa40b2332b6 100644 (file)
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -29,6 +29,7 @@ static char *dev_log_name;
 
 /* Path for the file where all log messages are written */
 static const char *logFilePath = "/var/log/messages";
+static int logFD = -1;
 
 /* interval between marks in seconds */
 static int markInterval = 20 * 60;
@@ -41,9 +42,11 @@ static char localHostName[64];
 
 #if ENABLE_FEATURE_ROTATE_LOGFILE
 /* max size of message file before being rotated */
-static int logFileSize = 200 * 1024;
+static unsigned logFileSize = 200 * 1024;
 /* number of rotated message files */
-static int logFileRotate = 1;
+static unsigned logFileRotate = 1;
+static unsigned curFileSize;
+static smallint isRegular;
 #endif
 
 #if ENABLE_FEATURE_REMOTE_LOG
@@ -256,7 +259,10 @@ void log_to_shmem(const char *msg);
 /* Print a message to the log file. */
 static void log_locally(char *msg)
 {
-       int fd, len = strlen(msg);
+       static time_t last;
+
+       struct flock fl;
+       int len = strlen(msg);
 
 #if ENABLE_FEATURE_IPC_SYSLOG
        if ((option_mask32 & OPT_circularlog) && shbuf) {
@@ -264,62 +270,69 @@ static void log_locally(char *msg)
                return;
        }
 #endif
-
- again:
-       fd = device_open(logFilePath, O_WRONLY | O_CREAT
+       if (logFD >= 0) {
+               time_t cur;
+               time(&cur);
+               if (last != cur) {
+                       last = cur; /* reopen log file every second */
+                       close(logFD);
+                       goto reopen;
+               }
+       } else {
+               struct stat statf;
+ reopen:
+               logFD = device_open(logFilePath, O_WRONLY | O_CREAT
                                        | O_NOCTTY | O_APPEND | O_NONBLOCK);
-       if (fd >= 0) {
-               struct flock fl;
+               if (logFD < 0) {
+                       /* cannot open logfile? - print to /dev/console then */
+                       int fd = device_open(_PATH_CONSOLE, O_WRONLY | O_NOCTTY | O_NONBLOCK);
+                       if (fd < 0)
+                               fd = 2; /* then stderr, dammit */
+                       full_write(fd, msg, len);
+                       if (fd != 2)
+                               close(fd);
+                       return;
+               }
+#if ENABLE_FEATURE_ROTATE_LOGFILE
+               isRegular = (fstat(logFD, &statf) == 0 && (statf.st_mode & S_IFREG));
+               /* bug (mostly harmless): can wrap around if file > 4gb */
+               curFileSize = statf.st_size;
+#endif
+       }
 
-               fl.l_whence = SEEK_SET;
-               fl.l_start = 0;
-               fl.l_len = 1;
-               fl.l_type = F_WRLCK;
-               fcntl(fd, F_SETLKW, &fl);
+       fl.l_whence = SEEK_SET;
+       fl.l_start = 0;
+       fl.l_len = 1;
+       fl.l_type = F_WRLCK;
+       fcntl(logFD, F_SETLKW, &fl);
 
 #if ENABLE_FEATURE_ROTATE_LOGFILE
-               if (logFileSize) {
-                       struct stat statf;
-                       int r = fstat(fd, &statf);
-                       if (!r && (statf.st_mode & S_IFREG)
-                        && (lseek(fd, 0, SEEK_END) > logFileSize)
-                       ) {
-                               if (logFileRotate) { /* always 0..99 */
-                                       int i = strlen(logFilePath) + 3 + 1;
-                                       char oldFile[i];
-                                       char newFile[i];
-                                       i = logFileRotate - 1;
-                                       /* rename: f.8 -> f.9; f.7 -> f.8; ... */
-                                       while (1) {
-                                               sprintf(newFile, "%s.%d", logFilePath, i);
-                                               if (i == 0) break;
-                                               sprintf(oldFile, "%s.%d", logFilePath, --i);
-                                               rename(oldFile, newFile);
-                                       }
-                                       /* newFile == "f.0" now */
-                                       rename(logFilePath, newFile);
-                                       fl.l_type = F_UNLCK;
-                                       fcntl(fd, F_SETLKW, &fl);
-                                       close(fd);
-                                       goto again;
-                               }
-                               ftruncate(fd, 0);
+       if (logFileSize && isRegular && curFileSize > logFileSize) {
+               if (logFileRotate) { /* always 0..99 */
+                       int i = strlen(logFilePath) + 3 + 1;
+                       char oldFile[i];
+                       char newFile[i];
+                       i = logFileRotate - 1;
+                       /* rename: f.8 -> f.9; f.7 -> f.8; ... */
+                       while (1) {
+                               sprintf(newFile, "%s.%d", logFilePath, i);
+                               if (i == 0) break;
+                               sprintf(oldFile, "%s.%d", logFilePath, --i);
+                               rename(oldFile, newFile);
                        }
+                       /* newFile == "f.0" now */
+                       rename(logFilePath, newFile);
+                       fl.l_type = F_UNLCK;
+                       fcntl(logFD, F_SETLKW, &fl);
+                       close(logFD);
+                       goto reopen;
                }
-#endif
-               full_write(fd, msg, len);
-               fl.l_type = F_UNLCK;
-               fcntl(fd, F_SETLKW, &fl);
-               close(fd);
-       } else {
-               /* cannot open logfile? - print to /dev/console then */
-               fd = device_open(_PATH_CONSOLE, O_WRONLY | O_NOCTTY | O_NONBLOCK);
-               if (fd < 0)
-                       fd = 2; /* then stderr, dammit */
-               full_write(fd, msg, len);
-               if (fd != 2)
-                       close(fd);
+               ftruncate(logFD, 0);
        }
+#endif
+       curFileSize += full_write(logFD, msg, len);
+       fl.l_type = F_UNLCK;
+       fcntl(logFD, F_SETLKW, &fl);
 }
 
 static void parse_fac_prio_20(int pri, char *res20)