(CC Peter) On Wed, 2014-07-02 at 15:41 +0900, Yasuaki Ishimatsu wrote: > llc_shared_mask is not cleared even if cpu is offline or hot removed. > So when hot-plugging CPU, the mask has wrong value. The mask is used > by CSF schduler. So it breaks CFS scheduler. > > Here is a example on my system. > My system has 4 sockets and each socket has 15 cores and HT is enabled. > In this case, each core of sockes is numbered as follows: > > | CPU# > Socket#0 | 0-14 , 60-74 > Socket#1 | 15-29, 75-89 > Socket#2 | 30-44, 90-104 > Socket#3 | 45-59, 105-119 > > Then llc_shared_mask of CPU#30 has 0x3fff80000001fffc0000000. > It means that cache of Socket#2 is shared with CPU#30-44 and 90-104. > > When hot-removing socket#2 and #3, each core of sockets is numbered > as follows: > > | CPU# > Socket#0 | 0-14 , 60-74 > Socket#1 | 15-29, 75-89 > > But llc_shared_mask is not cleared. So llc_shared_mask of CPU#30 remains > having 0x3fff80000001fffc0000000. > > After that, when hot-adding socket#2 and #3, each core of sockets is > numbered as follows: > > | CPU# > Socket#0 | 0-14 , 60-74 > Socket#1 | 15-29, 75-89 > Socket#2 | 30-59 > Socket#3 | 90-119 > > Then llc_shared_mask of CPU#30 becomes 0x3fff8000fffffffc0000000. > It means that cache of Socket#2 is shared with CPU#30-59 and 90-104. > So the mask has wrong value. > > This patch fixes above problem by clearing llc_shared_mask bit of > offlined cpu. > > Signed-off-by: Yasuaki Ishimatsu <[email protected]> > --- > arch/x86/kernel/smpboot.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 5492798..893cd2b 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1279,6 +1279,7 @@ __init void prefill_possible_map(void) > static void remove_siblinginfo(int cpu) > { > int sibling; > + int llc_shared; > struct cpuinfo_x86 *c = &cpu_data(cpu); > > for_each_cpu(sibling, cpu_core_mask(cpu)) { > @@ -1290,9 +1291,12 @@ static void remove_siblinginfo(int cpu) > cpu_data(sibling).booted_cores--; > } > > + for_each_cpu(llc_shared, cpu_llc_shared_mask(cpu)) > + cpumask_clear_cpu(cpu, cpu_llc_shared_mask(llc_shared)); > for_each_cpu(sibling, cpu_sibling_mask(cpu)) > cpumask_clear_cpu(cpu, cpu_sibling_mask(sibling)); > cpumask_clear(cpu_sibling_mask(cpu)); > + cpumask_clear(cpu_llc_shared_mask(cpu)); > cpumask_clear(cpu_core_mask(cpu)); > c->phys_proc_id = 0; > c->cpu_core_id = 0; > > -- > 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/
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