sched: document profile=sleep requiring CONFIG_SCHEDSTATS

profile=sleep only works if CONFIG_SCHEDSTATS is set. This patch notes
the limitation in Documentation/kernel-parameters.txt and prints a
warning at boot-time if profile=sleep is used without CONFIG_SCHEDSTAT.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a13d69b..8ae5fac 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1444,7 +1444,8 @@ and is between 256 and 4096 characters. It is defined in the file
                        Param: "schedule" - profile schedule points.
                        Param: <number> - step/bucket size as a power of 2 for
                                statistical time based profiling.
-                       Param: "sleep" - profile D-state sleeping (millisecs)
+                       Param: "sleep" - profile D-state sleeping (millisecs).
+                               Requires CONFIG_SCHEDSTATS
                        Param: "kvm" - profile VM exits.
 
        processor.max_cstate=   [HW,ACPI]

diff --git a/kernel/profile.c b/kernel/profile.c
index 631b75c..5e95330 100644 (file)
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -60,6 +60,7 @@ static int __init profile_setup(char * str)
        int par;
 
        if (!strncmp(str, sleepstr, strlen(sleepstr))) {
+#ifdef CONFIG_SCHEDSTATS
                prof_on = SLEEP_PROFILING;
                if (str[strlen(sleepstr)] == ',')
                        str += strlen(sleepstr) + 1;
@@ -68,6 +69,10 @@ static int __init profile_setup(char * str)
                printk(KERN_INFO
                        "kernel sleep profiling enabled (shift: %ld)\n",
                        prof_shift);
+#else
+               printk(KERN_WARNING
+                       "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
+#endif /* CONFIG_SCHEDSTATS */
        } else if (!strncmp(str, schedstr, strlen(schedstr))) {
                prof_on = SCHED_PROFILING;
                if (str[strlen(schedstr)] == ',')