X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/28d1ee2cda01bccdd2424f8fdbb4a924de37eaa3..d310fbedabd3101505b694f5c25a2e48480a3c2b:/src/syncio.c

diff --git a/src/syncio.c b/src/syncio.c
index b0c2969e..0c202c9e 100644
--- a/src/syncio.c
+++ b/src/syncio.c
@@ -42,10 +42,10 @@
 
 #define REDIS_SYNCIO_RESOLUTION 10 /* Resolution in milliseconds */
 
-/* Write the specified payload to 'fd'. If writing the whole payload will be done
- * within 'timeout' milliseconds the operation succeeds and 'size' is returned.
- * Otherwise the operation fails, -1 is returned, and an unspecified partial write
- * could be performed against the file descriptor. */
+/* Write the specified payload to 'fd'. If writing the whole payload will be
+ * done within 'timeout' milliseconds the operation succeeds and 'size' is
+ * returned. Otherwise the operation fails, -1 is returned, and an unspecified
+ * partial write could be performed against the file descriptor. */
 ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) {
     ssize_t nwritten, ret = size;
     long long start = mstime();
@@ -56,13 +56,19 @@ ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) {
                           remaining : REDIS_SYNCIO_RESOLUTION;
         long long elapsed;
 
-        if (aeWait(fd,AE_WRITABLE,wait) & AE_WRITABLE) {
-            nwritten = write(fd,ptr,size);
-            if (nwritten == -1) return -1;
+        /* Optimistically try to write before checking if the file descriptor
+         * is actually writable. At worst we get EAGAIN. */
+        nwritten = write(fd,ptr,size);
+        if (nwritten == -1) {
+            if (errno != EAGAIN) return -1;
+        } else {
             ptr += nwritten;
             size -= nwritten;
-            if (size == 0) return ret;
         }
+        if (size == 0) return ret;
+
+        /* Wait */
+        aeWait(fd,AE_WRITABLE,wait);
         elapsed = mstime() - start;
         if (elapsed >= timeout) {
             errno = ETIMEDOUT;
@@ -72,8 +78,8 @@ ssize_t syncWrite(int fd, char *ptr, ssize_t size, long long timeout) {
     }
 }
 
-/* Read the specified amount of bytes from 'fd'. If all the bytes are read within
- * 'timeout' milliseconds the operation succeed and 'size' is returned.
+/* Read the specified amount of bytes from 'fd'. If all the bytes are read
+ * within 'timeout' milliseconds the operation succeed and 'size' is returned.
  * Otherwise the operation fails, -1 is returned, and an unspecified amount of
  * data could be read from the file descriptor. */
 ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout) {
@@ -81,19 +87,27 @@ ssize_t syncRead(int fd, char *ptr, ssize_t size, long long timeout) {
     long long start = mstime();
     long long remaining = timeout;
 
+    if (size == 0) return 0;
     while(1) {
         long long wait = (remaining > REDIS_SYNCIO_RESOLUTION) ?
                           remaining : REDIS_SYNCIO_RESOLUTION;
         long long elapsed;
 
-        if (aeWait(fd,AE_READABLE,wait) & AE_READABLE) {
-            nread = read(fd,ptr,size);
-            if (nread <= 0) return -1;
+        /* Optimistically try to read before checking if the file descriptor
+         * is actually readable. At worst we get EAGAIN. */
+        nread = read(fd,ptr,size);
+        if (nread == 0) return -1; /* short read. */
+        if (nread == -1) {
+            if (errno != EAGAIN) return -1;
+        } else {
             ptr += nread;
             size -= nread;
             totread += nread;
-            if (size == 0) return totread;
         }
+        if (size == 0) return totread;
+
+        /* Wait */
+        aeWait(fd,AE_READABLE,wait);
         elapsed = mstime() - start;
         if (elapsed >= timeout) {
             errno = ETIMEDOUT;