[PATCH] Support for CFS SCHED_IDLE priority in chrt

[Martin Steigerwald <ms@teamix.de>]

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Please keep CC to linux-kernel or CC to me personally as I am not subscribed 
to util-linux-ng.

Hi!

Since I do not dare to break kernel code[1], I try the same with userspace 
code. The following patch should add SCHED_IDLE support to chrt. Beware it is 
complety untested, since I get:

ms@mango> autoconf      ~/lokal/Kernel/Dokumentation/util-linux-ng
configure.ac:7: error: possibly undefined macro: AM_INIT_AUTOMAKE
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
configure.ac:37: error: possibly undefined macro: AM_CONDITIONAL
configure.ac:190: error: possibly undefined macro: AM_GNU_GETTEXT_VERSION
configure.ac:191: error: possibly undefined macro: AM_GNU_GETTEXT
ms@mango> ./configure      ~/lokal/Kernel/Dokumentation/util-linux-ng
configure: error: cannot find install-sh or install.sh in config "."/config

when trying to compile util-linux-ng from GIT. (Note: I have no glue about 
autoconf, I only ever started an pre-existing ./configure script). I tried 
with autoconf 2.61-8 from Debian Lenny.

I will test this commit if someone gives me a hint on how to compile 
util-linux-ng.

[1] http://marc.info/?l=linux-kernel&m=122217132330769&w=2

---
From 8c6c5154bc5b53c0ccad8faa0ee3fe07bae447a5 Mon Sep 17 00:00:00 2001
From: Martin Steigerwald <ms@teamix.de>
Date: Tue, 23 Sep 2008 14:23:03 +0200
Subject: [PATCH] Support CFS SCHED_IDLE priority and document it

Support CFS_SCHED_IDLE priority and document it.

Beware, this is completely untested, since I autoconf 2.61-8 from Debian
Lenny produced errors.

Signed-off-by: Martin Steigerwald <ms@teamix.de>
---
 schedutils/chrt.1 |   11 +++++++++--
 schedutils/chrt.c |   23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/schedutils/chrt.1 b/schedutils/chrt.1
index dbc2958..67a9421 100644
--- a/schedutils/chrt.1
+++ b/schedutils/chrt.1
@@ -45,13 +45,16 @@ runs COMMAND with the given attributes.  Both policy (one 
of
 .BR SCHED_OTHER ,
 .BR SCHED_FIFO ,
 .BR SCHED_RR ,
+.BR SCHED_BATCH,
 or
-.BR SCHED_BATCH )
+.BR SCHED_IDLE)
 and priority can be set and retrieved.
 .PP
 The
 .BR SCHED_BATCH
-policy is supported since Linux 2.6.16.
+policy is supported since Linux 2.6.16. The
+.BR SCHED_IDLE
+policy is supported since Linux 2.6.23.
 .SH OPTIONS
 .TP
 .B -p, --pid
@@ -65,6 +68,10 @@ set scheduling policy to
 set scheduling policy to
 .BR SCHED_FIFO
 .TP
+.B -i, --idle
+set schedulng policy to
+.BR SCHED_IDLE
+.TP
 .B -m, --max
 show minimum and maximum valid priorities, then exit
 .TP
diff --git a/schedutils/chrt.c b/schedutils/chrt.c
index ba07dbe..5da8f6b 100644
--- a/schedutils/chrt.c
+++ b/schedutils/chrt.c
@@ -35,6 +35,14 @@
 # define SCHED_BATCH 3
 #endif
 
+/* the SCHED_IDLE is supported since Linux 2.6.23
+ * commit id 0e6aca43e08a62a48d6770e9a159dbec167bf4c6
+ * -- temporary workaround for people with old glibc headers
+ */
+#ifndef SCHED_IDLE
+# define SCHED_IDLE 5
+#endif
+
 static void show_usage(const char *cmd)
 {
 	fprintf(stderr, "chrt (%s)\n", PACKAGE_STRING);
@@ -45,6 +53,8 @@ static void show_usage(const char *cmd)
 			"set policy to SCHED_BATCH\n");
 	fprintf(stderr, "  -f, --fifo                         "
 			"set policy to SCHED_FIFO\n");
+	fprintf(stderr, "  -i, --idle                         "
+			"set policy to SCHED_IDLE\n");
 	fprintf(stderr, "  -p, --pid                          "
 			"operate on existing given pid\n");
 	fprintf(stderr, "  -m, --max                          "
@@ -87,6 +97,8 @@ static void show_rt_info(const char *what, pid_t pid)
 	case SCHED_FIFO:
 		printf("SCHED_FIFO\n");
 		break;
+	case SCHED_IDLE:
+		printf("SCHED_IDLE\n");
 	case SCHED_RR:
 		printf("SCHED_RR\n");
 		break;
@@ -138,6 +150,13 @@ static void show_min_max(void)
 		printf("SCHED_BATCH min/max priority\t: %d/%d\n", min, max);
 	else
 		printf("SCHED_BATCH not supported?\n");
+
+	max = sched_get_priority_max(SCHED_IDLE);
+	min = sched_get_priority_min(SCHED_IDLE);
+	if (max >= 0 && min >= 0)
+		printf("SCHED_IDLE min/max priority\t: %d/%d\n", min, max);
+	else
+		printf("SCHED_IDLE not supported?\n");
 }
 
 int main(int argc, char *argv[])
@@ -149,6 +168,7 @@ int main(int argc, char *argv[])
 	struct option longopts[] = {
 		{ "batch",	0, NULL, 'b' },
 		{ "fifo",	0, NULL, 'f' },
+		{ "idle",	0, NULL, 'i' },
 		{ "pid",	0, NULL, 'p' },
 		{ "help",	0, NULL, 'h' },
 		{ "max",        0, NULL, 'm' },
@@ -170,6 +190,9 @@ int main(int argc, char *argv[])
 		case 'f':
 			policy = SCHED_FIFO;
 			break;
+		case 'i':
+			policy = SCHED_IDLE;
+			break;
 		case 'm':
 			show_min_max();
 			return 0;

-- 
Martin Steigerwald - team(ix) GmbH - http://www.teamix.de
gpg: 19E3 8D42 896F D004 08AC A0CA 1E10 C593 0399 AE90

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