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

[lttng-tools.git] / src / bin / lttng / commands / enable_channels.c

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",