| Message ID | 20250218141018.18082-2-yangyicong@huawei.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Support SMT control on arm64 | expand |
On 18/02/2025 15:10, Yicong Yang wrote: > From: Yicong Yang <yangyicong@hisilicon.com> [...] > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 52f5850730b3..b3aba443c4eb 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) > } > #endif > > +#ifndef topology_is_primary_thread > + > +#define topology_is_primary_thread topology_is_primary_thread > + > +static inline bool topology_is_primary_thread(unsigned int cpu) > +{ > + /* > + * On SMT hotplug the primary thread of the SMT won't be disabled. > + * Architectures do have a special primary thread (e.g. x86) need > + * to override this function. Otherwise just make the first thread > + * in the SMT as the primary thread. > + * > + * The sibling cpumask of an offline CPU contains always the CPU > + * itself for architectures using CONFIG_GENERIC_ARCH_TOPOLOGY. > + * Other architectures should use this depend on their own > + * situation. This sentence is hard to get. Do you want to say that other architectures (CONFIG_GENERIC_ARCH_TOPOLOGY or !CONFIG_GENERIC_ARCH_TOPOLOGY) have to check whether they can use this default implementation or have to override it? [...]
On Tue, Feb 18, 2025 at 10:10:15PM +0800, Yicong Yang wrote: > From: Yicong Yang <yangyicong@hisilicon.com> > > Currently if architectures want to support HOTPLUG_SMT they need to > provide a topology_is_primary_thread() telling the framework which > thread in the SMT cannot offline. However arm64 doesn't have a > restriction on which thread in the SMT cannot offline, a simplest > choice is that just make 1st thread as the "primary" thread. So > just make this as the default implementation in the framework and > let architectures like x86 that have special primary thread to > override this function (which they've already done). > > There's no need to provide a stub function if !CONFIG_SMP or > !CONFIG_HOTPLUG_SMT. In such case the testing CPU is already > the 1st CPU in the SMT so it's always the primary thread. > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > --- > Pre questioned in v9 [1] whether this works on architectures not using > CONFIG_GENERIC_ARCH_TOPOLOGY, See [2] for demonstration hacking on LoongArch > VM and this also works. Architectures should use this on their own situation. > [1] https://lore.kernel.org/linux-arm-kernel/427bd639-33c3-47e4-9e83-68c428eb1a7d@arm.com/ > [2] https://lore.kernel.org/linux-arm-kernel/a5690fee-3019-f26c-8bad-1d95e388e877@huawei.com/ > > arch/powerpc/include/asm/topology.h | 1 + > arch/x86/include/asm/topology.h | 2 +- > include/linux/topology.h | 22 ++++++++++++++++++++++ > 3 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h > index 16bacfe8c7a2..da15b5efe807 100644 > --- a/arch/powerpc/include/asm/topology.h > +++ b/arch/powerpc/include/asm/topology.h > @@ -152,6 +152,7 @@ static inline bool topology_is_primary_thread(unsigned int cpu) > { > return cpu == cpu_first_thread_sibling(cpu); > } > +#define topology_is_primary_thread topology_is_primary_thread > > static inline bool topology_smt_thread_allowed(unsigned int cpu) > { > diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h > index ec134b719144..6c79ee7c0957 100644 > --- a/arch/x86/include/asm/topology.h > +++ b/arch/x86/include/asm/topology.h > @@ -229,11 +229,11 @@ static inline bool topology_is_primary_thread(unsigned int cpu) > { > return cpumask_test_cpu(cpu, cpu_primary_thread_mask); > } > +#define topology_is_primary_thread topology_is_primary_thread > > #else /* CONFIG_SMP */ > static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } > static inline int topology_max_smt_threads(void) { return 1; } > -static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } > static inline unsigned int topology_amd_nodes_per_pkg(void) { return 1; } > #endif /* !CONFIG_SMP */ > > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 52f5850730b3..b3aba443c4eb 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) > } > #endif > > +#ifndef topology_is_primary_thread > + > +#define topology_is_primary_thread topology_is_primary_thread > + > +static inline bool topology_is_primary_thread(unsigned int cpu) > +{ > + /* > + * On SMT hotplug the primary thread of the SMT won't be disabled. I may be misunderstanding the term "SMT hotplug" above. For me it is comparable with logical CPU hotplug, so the above statement may be misleading. IIUC, what you mean above is if SMT is disabled, the primary thread will always remain enabled/active. Does that make sense or am I missing something ? -- Regards, Sudeep
On 2025/2/28 19:10, Dietmar Eggemann wrote: > On 18/02/2025 15:10, Yicong Yang wrote: >> From: Yicong Yang <yangyicong@hisilicon.com> > > [...] > >> diff --git a/include/linux/topology.h b/include/linux/topology.h >> index 52f5850730b3..b3aba443c4eb 100644 >> --- a/include/linux/topology.h >> +++ b/include/linux/topology.h >> @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) >> } >> #endif >> >> +#ifndef topology_is_primary_thread >> + >> +#define topology_is_primary_thread topology_is_primary_thread >> + >> +static inline bool topology_is_primary_thread(unsigned int cpu) >> +{ >> + /* >> + * On SMT hotplug the primary thread of the SMT won't be disabled. >> + * Architectures do have a special primary thread (e.g. x86) need >> + * to override this function. Otherwise just make the first thread >> + * in the SMT as the primary thread. >> + * >> + * The sibling cpumask of an offline CPU contains always the CPU >> + * itself for architectures using CONFIG_GENERIC_ARCH_TOPOLOGY. >> + * Other architectures should use this depend on their own >> + * situation. > > This sentence is hard to get. Do you want to say that other > architectures (CONFIG_GENERIC_ARCH_TOPOLOGY or > !CONFIG_GENERIC_ARCH_TOPOLOGY) have to check whether they can use this > default implementation or have to override it? > yes exactly, will improve the comments. thanks.
On 2025/2/28 21:54, Sudeep Holla wrote: > On Tue, Feb 18, 2025 at 10:10:15PM +0800, Yicong Yang wrote: >> From: Yicong Yang <yangyicong@hisilicon.com> >> >> Currently if architectures want to support HOTPLUG_SMT they need to >> provide a topology_is_primary_thread() telling the framework which >> thread in the SMT cannot offline. However arm64 doesn't have a >> restriction on which thread in the SMT cannot offline, a simplest >> choice is that just make 1st thread as the "primary" thread. So >> just make this as the default implementation in the framework and >> let architectures like x86 that have special primary thread to >> override this function (which they've already done). >> >> There's no need to provide a stub function if !CONFIG_SMP or >> !CONFIG_HOTPLUG_SMT. In such case the testing CPU is already >> the 1st CPU in the SMT so it's always the primary thread. >> >> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> >> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> >> --- >> Pre questioned in v9 [1] whether this works on architectures not using >> CONFIG_GENERIC_ARCH_TOPOLOGY, See [2] for demonstration hacking on LoongArch >> VM and this also works. Architectures should use this on their own situation. >> [1] https://lore.kernel.org/linux-arm-kernel/427bd639-33c3-47e4-9e83-68c428eb1a7d@arm.com/ >> [2] https://lore.kernel.org/linux-arm-kernel/a5690fee-3019-f26c-8bad-1d95e388e877@huawei.com/ >> >> arch/powerpc/include/asm/topology.h | 1 + >> arch/x86/include/asm/topology.h | 2 +- >> include/linux/topology.h | 22 ++++++++++++++++++++++ >> 3 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h >> index 16bacfe8c7a2..da15b5efe807 100644 >> --- a/arch/powerpc/include/asm/topology.h >> +++ b/arch/powerpc/include/asm/topology.h >> @@ -152,6 +152,7 @@ static inline bool topology_is_primary_thread(unsigned int cpu) >> { >> return cpu == cpu_first_thread_sibling(cpu); >> } >> +#define topology_is_primary_thread topology_is_primary_thread >> >> static inline bool topology_smt_thread_allowed(unsigned int cpu) >> { >> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h >> index ec134b719144..6c79ee7c0957 100644 >> --- a/arch/x86/include/asm/topology.h >> +++ b/arch/x86/include/asm/topology.h >> @@ -229,11 +229,11 @@ static inline bool topology_is_primary_thread(unsigned int cpu) >> { >> return cpumask_test_cpu(cpu, cpu_primary_thread_mask); >> } >> +#define topology_is_primary_thread topology_is_primary_thread >> >> #else /* CONFIG_SMP */ >> static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } >> static inline int topology_max_smt_threads(void) { return 1; } >> -static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } >> static inline unsigned int topology_amd_nodes_per_pkg(void) { return 1; } >> #endif /* !CONFIG_SMP */ >> >> diff --git a/include/linux/topology.h b/include/linux/topology.h >> index 52f5850730b3..b3aba443c4eb 100644 >> --- a/include/linux/topology.h >> +++ b/include/linux/topology.h >> @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) >> } >> #endif >> >> +#ifndef topology_is_primary_thread >> + >> +#define topology_is_primary_thread topology_is_primary_thread >> + >> +static inline bool topology_is_primary_thread(unsigned int cpu) >> +{ >> + /* >> + * On SMT hotplug the primary thread of the SMT won't be disabled. > > I may be misunderstanding the term "SMT hotplug" above. For me it is > comparable with logical CPU hotplug, so the above statement may be > misleading. IIUC, what you mean above is if SMT is disabled, the > primary thread will always remain enabled/active. Does that make sense > or am I missing something ? > I just the borrow the term from kconfig HOTPLUG_SMT here, but here the statement only involves the disable part, so maybe it'll be more accurate to use "SMT disable" rather than "SMT hotplug" here? Thanks.
diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h index 16bacfe8c7a2..da15b5efe807 100644 --- a/arch/powerpc/include/asm/topology.h +++ b/arch/powerpc/include/asm/topology.h @@ -152,6 +152,7 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpu == cpu_first_thread_sibling(cpu); } +#define topology_is_primary_thread topology_is_primary_thread static inline bool topology_smt_thread_allowed(unsigned int cpu) { diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index ec134b719144..6c79ee7c0957 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -229,11 +229,11 @@ static inline bool topology_is_primary_thread(unsigned int cpu) { return cpumask_test_cpu(cpu, cpu_primary_thread_mask); } +#define topology_is_primary_thread topology_is_primary_thread #else /* CONFIG_SMP */ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; } static inline int topology_max_smt_threads(void) { return 1; } -static inline bool topology_is_primary_thread(unsigned int cpu) { return true; } static inline unsigned int topology_amd_nodes_per_pkg(void) { return 1; } #endif /* !CONFIG_SMP */ diff --git a/include/linux/topology.h b/include/linux/topology.h index 52f5850730b3..b3aba443c4eb 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -240,6 +240,28 @@ static inline const struct cpumask *cpu_smt_mask(int cpu) } #endif +#ifndef topology_is_primary_thread + +#define topology_is_primary_thread topology_is_primary_thread + +static inline bool topology_is_primary_thread(unsigned int cpu) +{ + /* + * On SMT hotplug the primary thread of the SMT won't be disabled. + * Architectures do have a special primary thread (e.g. x86) need + * to override this function. Otherwise just make the first thread + * in the SMT as the primary thread. + * + * The sibling cpumask of an offline CPU contains always the CPU + * itself for architectures using CONFIG_GENERIC_ARCH_TOPOLOGY. + * Other architectures should use this depend on their own + * situation. + */ + return cpu == cpumask_first(topology_sibling_cpumask(cpu)); +} + +#endif + static inline const struct cpumask *cpu_cpu_mask(int cpu) { return cpumask_of_node(cpu_to_node(cpu));