[patch 1/3] s390: smp initialization speed

[patch 1/3] s390: smp initialization speed

[Heiko Carstens]

From: Heiko Carstens <heiko.carstens@de.ibm.com>

The last changes that introduced the additional_cpus command line parameter
also introduced a regression regarding smp initialization speed. In
smp_setup_cpu_possible_map() cpu_present_map is set to the same value
as cpu_possible_map. Especially that means that bits in the present map
will be set for cpus that are not present. This will cause a slow down
in the initial cpu_up() loop in smp_init() since trying to take cpus online
that aren't present takes a while.
Fix this by setting only bits for present cpus in cpu_present_map and
set cpu_present_map to cpu_possible_map in smp_cpus_done().

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---

 arch/s390/kernel/smp.c |   15 ++++++++++-----
 1 files changed, 10 insertions(+), 5 deletions(-)

diff -urpN linux-2.6/arch/s390/kernel/smp.c linux-2.6-patched/arch/s390/kernel/smp.c
--- linux-2.6/arch/s390/kernel/smp.c	2006-02-16 17:10:59.000000000 +0100
+++ linux-2.6-patched/arch/s390/kernel/smp.c	2006-02-16 17:10:59.000000000 +0100
@@ -677,17 +677,21 @@ static unsigned int __initdata possible_
 
 void __init smp_setup_cpu_possible_map(void)
 {
-	unsigned int pcpus, cpu;
+	unsigned int phy_cpus, pos_cpus, cpu;
 
-	pcpus = min(smp_count_cpus() + additional_cpus, (unsigned int) NR_CPUS);
+	phy_cpus = smp_count_cpus();
+	pos_cpus = min(phy_cpus + additional_cpus, (unsigned int) NR_CPUS);
 
 	if (possible_cpus)
-		pcpus = min(possible_cpus, (unsigned int) NR_CPUS);
+		pos_cpus = min(possible_cpus, (unsigned int) NR_CPUS);
 
-	for (cpu = 0; cpu < pcpus; cpu++)
+	for (cpu = 0; cpu < pos_cpus; cpu++)
 		cpu_set(cpu, cpu_possible_map);
 
-	cpu_present_map = cpu_possible_map;
+	phy_cpus = min(phy_cpus, pos_cpus);
+
+	for (cpu = 0; cpu < phy_cpus; cpu++)
+		cpu_set(cpu, cpu_present_map);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -843,6 +847,7 @@ void __devinit smp_prepare_boot_cpu(void
 
 void smp_cpus_done(unsigned int max_cpus)
 {
+	cpu_present_map = cpu_possible_map;
 }
 
 /*