blktrace: Document default values for -b and -n

To help users better deal with the log message
 "You have dropped events, consider using a larger buffer size (-b)",
it's helpful to list the defaults for sub buffer management, without
flags.

Signed-off-by: Justin TerAvest <teravest@google.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/blktrace.c b/blktrace.c
index 18c51579d2f708f9746945384f9fa20a104cd40d..72866e23457ec54899e562b7f985f975fd8cba49 100644 (file)
--- a/blktrace.c
+++ b/blktrace.c
@@ -460,8 +460,8 @@ static char usage_str[] = "\n\n" \
        "\t-w Stop after defined time, in seconds\n" \
        "\t-a Only trace specified actions. See documentation\n" \
        "\t-A Give trace mask as a single value. See documentation\n" \
-       "\t-b Sub buffer size in KiB\n" \
-       "\t-n Number of sub buffers\n" \
+       "\t-b Sub buffer size in KiB (default 512)\n" \
+       "\t-n Number of sub buffers (default 4)\n" \
        "\t-l Run in network listen mode (blktrace server)\n" \
        "\t-h Run in network client mode, connecting to the given host\n" \
        "\t-p Network port to use (default 8462)\n" \