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[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>
This commit is contained in:
Heiko Carstens 2006-02-17 13:52:48 -08:00 committed by Linus Torvalds
parent 37a3302618
commit 54330456b2
1 changed files with 10 additions and 5 deletions
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15
arch/s390/kernel/smp.c
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@ -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;
}
/*