[PATCH] s390: smp initialization speed

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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 5 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index d0a2745aec7f..7dbe00c76c6b 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -677,17 +677,21 @@ static unsigned int __initdata possible_cpus;
 
 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;
 }
 
 /*