[PATCH] s390: smp initialization speed (54330456) · Commits · 戴 / test

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>

arch/s390/kernel/smp.c

+10 −5

Original line number	Diff line number	Diff line
		@@ -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;
		}

		/*

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