From 1b25fda0533462c9cee3a22e8a7bea68fa670af2 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 19 Sep 2017 12:52:22 +0200 Subject: s390/topology: alternative topology for topology-less machines If running on machines that do not provide topology information we currently generate a "fake" topology which defines the maximum distance between each cpu: each cpu will be put into an own drawer. Historically this used to be the best option for (virtual) machines in overcommited hypervisors. For some workloads however it is better to generate a different topology where all cpus are siblings within a package (all cpus are core siblings). This shows performance improvements of up to 10%, depending on the workload. In order to keep the current behaviour, but also allow to switch to the different core sibling topology use the existing "topology=" kernel parameter: Specifying "topology=on" on machines without topology information will generate the core siblings (fake) topology information, instead of the default topology information where all cpus have the maximum distance. On machines which provide topology information specifying "topology=on" does not have any effect. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/early.c | 12 ------------ 1 file changed, 12 deletions(-) (limited to 'arch/s390/kernel/early.c') diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c index ca8cd80e8feb..60181caf8e8a 100644 --- a/arch/s390/kernel/early.c +++ b/arch/s390/kernel/early.c @@ -404,18 +404,6 @@ static inline void save_vector_registers(void) #endif } -static int __init topology_setup(char *str) -{ - bool enabled; - int rc; - - rc = kstrtobool(str, &enabled); - if (!rc && !enabled) - S390_lowcore.machine_flags &= ~MACHINE_FLAG_TOPOLOGY; - return rc; -} -early_param("topology", topology_setup); - static int __init disable_vector_extension(char *str) { S390_lowcore.machine_flags &= ~MACHINE_FLAG_VX; -- cgit v1.2.3-55-g7522