Messages in this thread Patch in this message | | | Date | Thu, 16 Feb 2006 17:40:17 +0100 | From | Heiko Carstens <> | Subject | [patch 1/3] s390: smp initialization speed |
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
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> ---
arch/s390/kernel/smp.c | 15 ++++++++++----- 1 files changed, 10 insertions(+), 5 deletions(-)
diff -urpN linux-2.6/arch/s390/kernel/smp.c linux-2.6-patched/arch/s390/kernel/smp.c --- linux-2.6/arch/s390/kernel/smp.c 2006-02-16 17:10:59.000000000 +0100 +++ linux-2.6-patched/arch/s390/kernel/smp.c 2006-02-16 17:10:59.000000000 +0100 @@ -677,17 +677,21 @@ static unsigned int __initdata possible_ 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; } /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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