Document that num-subbuf and subbuf-size need to be power of 2

Reported-by: Tan Dung Le Tran <tan.dung.le.tran@ericsson.com>
Acked-by: David Goulet <dgoulet@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/doc/man/lttng.1 b/doc/man/lttng.1
index 8416f4c21604b5cf5a05d56f272d60ff101f151a..2445b05ac1f9106e2f4089f94441001513a26560 100644 (file)
--- a/doc/man/lttng.1
+++ b/doc/man/lttng.1
@@ -274,8 +274,10 @@ file.
         Subbuffer size in bytes (default: 4096, kernel default: 262144)
 \-\-num-subbuf
         Number of subbufers (default: 8, kernel default: 4)
+        Needs to be a power of 2 for kernel and ust tracers
 \-\-switch-timer
         Switch subbuffer timer interval in usec (default: 0)
+        Needs to be a power of 2 for kernel and ust tracers
 \-\-read-timer
         Read timer interval in usec (default: 200)
 .fi

diff --git a/src/bin/lttng/commands/enable_channels.c b/src/bin/lttng/commands/enable_channels.c
index 91345e051247a6bed7d55be7df10ccee2cfcf023..4e56b3ca5f38b2ad87dec90291a8dc9438d9f3f2 100644 (file)
--- a/src/bin/lttng/commands/enable_channels.c
+++ b/src/bin/lttng/commands/enable_channels.c
@@ -104,10 +104,14 @@ static void usage(FILE *ofp)
        fprintf(ofp, "                               (default: %u, kernel default: %u)\n",
                DEFAULT_CHANNEL_SUBBUF_SIZE,
                DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE);
+       fprintf(ofp, "                               Needs to be a power of 2 for\n");
+        fprintf(ofp, "                               kernel and ust tracers\n");
        fprintf(ofp, "      --num-subbuf NUM     Number of subbufers\n");
        fprintf(ofp, "                               (default: %u, kernel default: %u)\n",
                DEFAULT_CHANNEL_SUBBUF_NUM,
                DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM);
+       fprintf(ofp, "                               Needs to be a power of 2 for\n");
+        fprintf(ofp, "                               kernel and ust tracers\n");
        fprintf(ofp, "      --switch-timer USEC  Switch timer interval in usec (default: %u)\n",
                DEFAULT_CHANNEL_SWITCH_TIMER);
        fprintf(ofp, "      --read-timer USEC    Read timer interval in usec (default: %u)\n",