[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>
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index d0a2745..7dbe00c 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -677,17 +677,21 @@
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 smp_cpus_done(unsigned int max_cpus)
{
+ cpu_present_map = cpu_possible_map;
}
/*