On 10/19/2015 11:04 AM, Prarit Bhargava wrote: > The information in /sys/devices/system/cpu/cpuX/topology > directory is useful for userspace monitoring applications and in-tree > utilities like cpupower & turbostat. > > When down'ing a CPU the /sys/devices/system/cpu/cpuX/topology directory is > removed during the CPU_DEAD hotplug callback in the kernel. The problem > with this model is that the CPU has not been physically removed and the > data in the topology directory is still valid. > > This patch adds CONFIG_PERMANENT_CPU_TOPOLOGY, and is Y by default for > x86, an N for all other arches. When enabled the kernel is modified so > that the topology directory is added to the core cpu sysfs files so that > the topology directory exists for the lifetime of the CPU. When > disabled, the behavior of the current kernel is maintained (that is, the > topology directory is removed on a down and added on an up). Adding > CONFIG_PERMANENT_CPU_TOPOLOGY may require additional architecture so that > the cpumask data the CPU's topology is not cleared during a CPU down. > > This patch combines drivers/base/topology.c and drivers/base/cpu.c to > implement CONFIG_PERMANENT_CPU_TOPOLOGY, and leaves all arches except > x86 with the current behavior. > > Before patch: > > [root@prarit cpu143]# ls > cache crash_notes firmware_node online thermal_throttle > cpufreq crash_notes_size microcode power topology > cpuidle driver node3 subsystem uevent > > Down a cpu > > [root@prarit cpu143]# echo 0 > online > > [root@intel-brickland-05 cpu143]# ls > cpuidle crash_notes_size firmware_node online subsystem > crash_notes driver node3 power uevent > [root@intel-brickland-05 cpu143]# ls -l topology > ls: cannot access topology: No such file or directory > > After patch: > > [root@prarit cpu143]# ls > cache crash_notes firmware_node online thermal_throttle > cpufreq crash_notes_size microcode power topology > cpuidle driver node3 subsystem uevent > [root@prarit cpu143]# cat topology/* > 27 > ffff,c0000000,000000ff,ffc00000,00000000 > 54-71,126-143 > 3 > 8000,00000000,00000080,00000000,00000000 > 71,143 > > Down a cpu > > [root@prarit cpu143]# echo 0 > online > [root@intel-brickland-05 cpu143]# ls > cpuidle crash_notes_size firmware_node online subsystem uevent > crash_notes driver node3 power topology > [root@prarit cpu143]# cat topology/* > 27 > ffff,c0000000,000000ff,ffc00000,00000000 > 54-71,126-143 > 3 > 8000,00000000,00000080,00000000,00000000 > 71,143 > > I did some light testing with and without BOOTPARAM_HOTPLUG_CPU0 enabled, > and up'd and down'd CPUs in sequence, randomly, by thread group, by > socket group and didn't see any issues. > > Cc: Thomas Gleixner <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: "H. Peter Anvin" <[email protected]> > Cc: [email protected] > Cc: Greg Kroah-Hartman <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Len Brown <[email protected]> > Cc: Andy Lutomirski <[email protected]> > Cc: Zhu Guihua <[email protected]> > Cc: Denys Vlasenko <[email protected]> > Cc: "Jan H. Schönherr" <[email protected]> > Cc: Boris Ostrovsky <[email protected]> > Cc: Prarit Bhargava <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > Cc: Thomas Renninger <[email protected]> > Signed-off-by: Prarit Bhargava <[email protected]> > --- > arch/x86/kernel/smpboot.c | 28 -------- > drivers/base/Kconfig | 13 ++++ > drivers/base/Makefile | 2 +- > drivers/base/cpu.c | 135 +++++++++++++++++++++++++++++++++++++++ > drivers/base/topology.c | 155 > --------------------------------------------- > 5 files changed, 149 insertions(+), 184 deletions(-) > delete mode 100644 drivers/base/topology.c > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index e0c198e..19082c7 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1322,32 +1322,6 @@ __init void prefill_possible_map(void) > > #ifdef CONFIG_HOTPLUG_CPU > > -static void remove_siblinginfo(int cpu) > -{ > - int sibling; > - struct cpuinfo_x86 *c = &cpu_data(cpu); > - > - for_each_cpu(sibling, topology_core_cpumask(cpu)) { > - cpumask_clear_cpu(cpu, topology_core_cpumask(sibling)); > - /*/ > - * last thread sibling in this cpu core going down > - */ > - if (cpumask_weight(topology_sibling_cpumask(cpu)) == 1) > - cpu_data(sibling).booted_cores--; > - } > - > - for_each_cpu(sibling, topology_sibling_cpumask(cpu)) > - cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling)); > - for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) > - cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling)); > - cpumask_clear(cpu_llc_shared_mask(cpu)); > - cpumask_clear(topology_sibling_cpumask(cpu)); > - cpumask_clear(topology_core_cpumask(cpu));
It was just pointed out to me that the these masks tend to be used in the kernel as "sibling & online mask", and "core & online_mask". The other values are indeed static and are safe to use. I'll "self-nak" this and come up with a slightly better patchset. P. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
