Improvements to make --bwlimit work better.

diff --git a/io.c b/io.c
index c9691ed..6028565 100644 (file)
--- a/io.c
+++ b/io.c
@@ -47,6 +47,7 @@ static time_t last_io;
 static int no_flush;
 
 extern int bwlimit;
+extern size_t bwlimit_writemax;
 extern int verbose;
 extern int io_timeout;
 extern int am_server;
@@ -739,22 +740,51 @@ unsigned char read_byte(int f)
  * use a bit less bandwidth than specified, because it doesn't make up
  * for slow periods.  But arguably this is a feature.  In addition, we
  * ought to take the time used to write the data into account.
+ *
+ * During some phases of big transfers (file FOO is uptodate) this is
+ * called with a small bytes_written every time.  As the kernel has to
+ * round small waits up to guarantee that we actually wait at least the
+ * requested number of microseconds, this can become grossly inaccurate.
+ * We therefore keep track of the bytes we've written over time and only
+ * sleep when the accumulated delay is at least 1 tenth of a second.
  **/
 static void sleep_for_bwlimit(int bytes_written)
 {
-       struct timeval tv;
+       static struct timeval prior_tv;
+       static long total_written = 0; 
+       struct timeval tv, start_tv;
+       long elapsed_usec, sleep_usec;
+
+#define ONE_SEC        1000000L /* # of microseconds in a second */
 
        if (!bwlimit)
                return;
 
-       assert(bytes_written > 0);
-       assert(bwlimit > 0);
+       total_written += bytes_written; 
+
+       gettimeofday(&start_tv, NULL);
+       if (prior_tv.tv_sec) {
+               elapsed_usec = (start_tv.tv_sec - prior_tv.tv_sec) * ONE_SEC
+                            + (start_tv.tv_usec - prior_tv.tv_usec);
+               total_written -= elapsed_usec * bwlimit / (ONE_SEC/1024);
+               if (total_written < 0)
+                       total_written = 0;
+       }
 
-       tv.tv_usec = bytes_written * 1000 / bwlimit;
-       tv.tv_sec  = tv.tv_usec / 1000000;
-       tv.tv_usec = tv.tv_usec % 1000000;
+       sleep_usec = total_written * (ONE_SEC/1024) / bwlimit;
+       if (sleep_usec < ONE_SEC / 10) {
+               prior_tv = start_tv;
+               return;
+       }
 
+       tv.tv_sec  = sleep_usec / ONE_SEC;
+       tv.tv_usec = sleep_usec % ONE_SEC;
        select(0, NULL, NULL, NULL, &tv);
+
+       gettimeofday(&prior_tv, NULL);
+       elapsed_usec = (prior_tv.tv_sec - start_tv.tv_sec) * ONE_SEC
+                    + (prior_tv.tv_usec - start_tv.tv_usec);
+       total_written = (sleep_usec - elapsed_usec) * bwlimit / (ONE_SEC/1024);
 }
 
 
@@ -812,6 +842,8 @@ static void writefd_unbuffered(int fd,char *buf,size_t len)
                if (FD_ISSET(fd, &w_fds)) {
                        int ret;
                        size_t n = len-total;
+                       if (bwlimit && n > bwlimit_writemax)
+                               n = bwlimit_writemax;
                        ret = write(fd,buf+total,n);
 
                        if (ret < 0) {