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Commit 54330456 authored by Heiko Carstens's avatar Heiko Carstens Committed by Linus Torvalds
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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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 37a33026

arch/s390/kernel/smp.c

+10 −5
Original line number Original line Diff line number Diff line
@@ -677,17 +677,21 @@ static unsigned int __initdata possible_cpus; 




void __init smp_setup_cpu_possible_map(void)

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)

	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_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

#ifdef CONFIG_HOTPLUG_CPU
@@ -843,6 +847,7 @@ void __devinit smp_prepare_boot_cpu(void) 




void smp_cpus_done(unsigned int max_cpus)

void smp_cpus_done(unsigned int max_cpus)

{

{

	cpu_present_map = cpu_possible_map;

}

}





/*

/*