Make "git clone" pack-fetching download statistics better

Average it out over a few events to make the numbers stable, and fix the
silly usec->binary-ms conversion.

Yeah, yeah, it's arguably eye-candy to keep the user calm, but let's do
that right.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/fetch-clone.c b/fetch-clone.c
index b67d976..873312d 100644 (file)
--- a/fetch-clone.c
+++ b/fetch-clone.c
@@ -130,12 +130,35 @@ int receive_unpack_pack(int fd[2], const char *me, int quiet)
        die("git-unpack-objects died of unnatural causes %d", status);
 }
 
+/*
+ * We average out the download speed over this many "events", where
+ * an event is a minimum of about half a second. That way, we get
+ * a reasonably stable number.
+ */
+#define NR_AVERAGE (4)
+
+/*
+ * A "binary msec" is a power-of-two-msec, aka 1/1024th of a second.
+ * Keeing the time in that format means that "bytes / msecs" means
+ * is the same as kB/s (modulo rounding).
+ *
+ * 1000512 is a magic number (usecs in a second, rounded up by half
+ * of 1024, to make "rounding" come out right ;)
+ */
+#define usec_to_binarymsec(x) ((int)(x) / (1000512 >> 10))
+
 int receive_keep_pack(int fd[2], const char *me, int quiet)
 {
        char tmpfile[PATH_MAX];
        int ofd, ifd;
        unsigned long total;
        static struct timeval prev_tv;
+       struct average {
+               unsigned long bytes;
+               unsigned long time;
+       } download[NR_AVERAGE] = { {0, 0}, };
+       unsigned long avg_bytes, avg_time;
+       int idx = 0;
 
        ifd = fd[0];
        snprintf(tmpfile, sizeof(tmpfile),
@@ -146,6 +169,8 @@ int receive_keep_pack(int fd[2], const char *me, int quiet)
 
        gettimeofday(&prev_tv, NULL);
        total = 0;
+       avg_bytes = 0;
+       avg_time = 0;
        while (1) {
                char buf[8192];
                ssize_t sz, wsz, pos;
@@ -181,14 +206,27 @@ int receive_keep_pack(int fd[2], const char *me, int quiet)
                        gettimeofday(&tv, NULL);
                        msecs = tv.tv_sec - prev_tv.tv_sec;
                        msecs <<= 10;
-                       msecs += (int)(tv.tv_usec - prev_tv.tv_usec) >> 10;
+                       msecs += usec_to_binarymsec(tv.tv_usec - prev_tv.tv_usec);
+
                        if (msecs > 500) {
                                prev_tv = tv;
                                last = total;
-                               fprintf(stderr, "%4lu.%03luMB  (%lu kB/s)        \r",
+
+                               /* Update averages ..*/
+                               avg_bytes += diff;
+                               avg_time += msecs;
+                               avg_bytes -= download[idx].bytes;
+                               avg_time -= download[idx].time;
+                               download[idx].bytes = diff;
+                               download[idx].time = msecs;
+                               idx++;
+                               if (idx >= NR_AVERAGE)
+                                       idx = 0;
+
+                               fprintf(stderr, "%4lu.%03luMB  (%lu kB/s)      \r",
                                        total >> 20,
                                        1000*((total >> 10) & 1023)>>10,
-                                       diff / msecs );
+                                       avg_bytes / avg_time );
                        }
                }
        }