| Message ID | 20190520090501.20415-1-anju@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | powerpc/perf: Use cpumask_last() to determine the | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (8150a153c013aa2dd1ffae43370b89ac1347a7fb) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 26 lines checked |
Hi, Somehow the subject of this patch didn't appear completely here. The Subject of this patch is as follows, `Subject [PATCH] powerpc/perf: Use cpumask_last() to determine the designated cpu for nest/core units.` Thanks, Anju On 5/20/19 2:35 PM, Anju T Sudhakar wrote: > Nest and core imc(In-memory Collection counters) assigns a particular > cpu as the designated target for counter data collection. > During system boot, the first online cpu in a chip gets assigned as > the designated cpu for that chip(for nest-imc) and the first online cpu > in a core gets assigned as the designated cpu for that core(for core-imc). > > If the designated cpu goes offline, the next online cpu from the same > chip(for nest-imc)/core(for core-imc) is assigned as the next target, > and the event context is migrated to the target cpu. > Currently, cpumask_any_but() function is used to find the target cpu. > Though this function is expected to return a `random` cpu, this always > returns the next online cpu. > > If all cpus in a chip/core is offlined in a sequential manner, starting > from the first cpu, the event migration has to happen for all the cpus > which goes offline. Since the migration process involves a grace period, > the total time taken to offline all the cpus will be significantly high. >
On 20/05/19 2:35 PM, Anju T Sudhakar wrote: > Nest and core imc(In-memory Collection counters) assigns a particular > cpu as the designated target for counter data collection. > During system boot, the first online cpu in a chip gets assigned as > the designated cpu for that chip(for nest-imc) and the first online cpu > in a core gets assigned as the designated cpu for that core(for core-imc). > > If the designated cpu goes offline, the next online cpu from the same > chip(for nest-imc)/core(for core-imc) is assigned as the next target, > and the event context is migrated to the target cpu. > Currently, cpumask_any_but() function is used to find the target cpu. > Though this function is expected to return a `random` cpu, this always > returns the next online cpu. > > If all cpus in a chip/core is offlined in a sequential manner, starting > from the first cpu, the event migration has to happen for all the cpus > which goes offline. Since the migration process involves a grace period, > the total time taken to offline all the cpus will be significantly high. > > Example: > In a system which has 2 sockets, with > NUMA node0 CPU(s): 0-87 > NUMA node8 CPU(s): 88-175 > > Time taken to offline cpu 88-175: > real 2m56.099s > user 0m0.191s > sys 0m0.000s > > Use cpumask_last() to choose the target cpu, when the designated cpu > goes online, so the migration will happen only when the last_cpu in the > mask goes offline. This way the time taken to offline all cpus in a > chip/core can be reduced. > > With the patch, > > Time taken to offline cpu 88-175: > real 0m12.207s > user 0m0.171s > sys 0m0.000s > > cpumask_last() is a better way to find the target cpu, since in most of the > cases cpuhotplug is performed in an increasing order(even in ppc64_cpu). > > cpumask_any_but() can still be used to check the possibility of other > online cpus from the same chip/core if the last cpu in the mask goes > offline. Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Also add "Fixes:" tag and this should go to stable right? > > Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com> > --- > arch/powerpc/perf/imc-pmu.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c > index 31fa753..fbfd6e7 100644 > --- a/arch/powerpc/perf/imc-pmu.c > +++ b/arch/powerpc/perf/imc-pmu.c > @@ -366,7 +366,14 @@ static int ppc_nest_imc_cpu_offline(unsigned int cpu) > */ > nid = cpu_to_node(cpu); > l_cpumask = cpumask_of_node(nid); > - target = cpumask_any_but(l_cpumask, cpu); > + target = cpumask_last(l_cpumask); > + > + /* > + * If this(target) is the last cpu in the cpumask for this chip, > + * check for any possible online cpu in the chip. > + */ > + if (unlikely(target == cpu)) > + target = cpumask_any_but(l_cpumask, cpu); > > /* > * Update the cpumask with the target cpu and > @@ -671,7 +678,10 @@ static int ppc_core_imc_cpu_offline(unsigned int cpu) > return 0; > > /* Find any online cpu in that core except the current "cpu" */ > - ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); > + ncpu = cpumask_last(cpu_sibling_mask(cpu)); > + > + if (unlikely(ncpu == cpu)) > + ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); > > if (ncpu >= 0 && ncpu < nr_cpu_ids) { > cpumask_set_cpu(ncpu, &core_imc_cpumask);
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c index 31fa753..fbfd6e7 100644 --- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -366,7 +366,14 @@ static int ppc_nest_imc_cpu_offline(unsigned int cpu) */ nid = cpu_to_node(cpu); l_cpumask = cpumask_of_node(nid); - target = cpumask_any_but(l_cpumask, cpu); + target = cpumask_last(l_cpumask); + + /* + * If this(target) is the last cpu in the cpumask for this chip, + * check for any possible online cpu in the chip. + */ + if (unlikely(target == cpu)) + target = cpumask_any_but(l_cpumask, cpu); /* * Update the cpumask with the target cpu and @@ -671,7 +678,10 @@ static int ppc_core_imc_cpu_offline(unsigned int cpu) return 0; /* Find any online cpu in that core except the current "cpu" */ - ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); + ncpu = cpumask_last(cpu_sibling_mask(cpu)); + + if (unlikely(ncpu == cpu)) + ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); if (ncpu >= 0 && ncpu < nr_cpu_ids) { cpumask_set_cpu(ncpu, &core_imc_cpumask);
Nest and core imc(In-memory Collection counters) assigns a particular cpu as the designated target for counter data collection. During system boot, the first online cpu in a chip gets assigned as the designated cpu for that chip(for nest-imc) and the first online cpu in a core gets assigned as the designated cpu for that core(for core-imc). If the designated cpu goes offline, the next online cpu from the same chip(for nest-imc)/core(for core-imc) is assigned as the next target, and the event context is migrated to the target cpu. Currently, cpumask_any_but() function is used to find the target cpu. Though this function is expected to return a `random` cpu, this always returns the next online cpu. If all cpus in a chip/core is offlined in a sequential manner, starting from the first cpu, the event migration has to happen for all the cpus which goes offline. Since the migration process involves a grace period, the total time taken to offline all the cpus will be significantly high. Example: In a system which has 2 sockets, with NUMA node0 CPU(s): 0-87 NUMA node8 CPU(s): 88-175 Time taken to offline cpu 88-175: real 2m56.099s user 0m0.191s sys 0m0.000s Use cpumask_last() to choose the target cpu, when the designated cpu goes online, so the migration will happen only when the last_cpu in the mask goes offline. This way the time taken to offline all cpus in a chip/core can be reduced. With the patch, Time taken to offline cpu 88-175: real 0m12.207s user 0m0.171s sys 0m0.000s cpumask_last() is a better way to find the target cpu, since in most of the cases cpuhotplug is performed in an increasing order(even in ppc64_cpu). cpumask_any_but() can still be used to check the possibility of other online cpus from the same chip/core if the last cpu in the mask goes offline. Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com> --- arch/powerpc/perf/imc-pmu.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)