| Message ID | 20230421141723.2405942-5-peternewman@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/resctrl: Use soft RMIDs for reliable MBM on AMD | expand |
Hi Peter, On 4/21/2023 7:17 AM, Peter Newman wrote: > To implement soft RMIDs, context switch must detect when the current > soft RMID is changing and if so, flush the CPU's MBM event counts to the > outgoing soft RMID. > > To avoid impacting context switch performance in the non-soft RMID case, > protect the new logic with a static branch. > > Co-developed-by: Stephane Eranian <eranian@google.com> > Signed-off-by: Stephane Eranian <eranian@google.com> > Signed-off-by: Peter Newman <peternewman@google.com> > --- > arch/x86/include/asm/resctrl.h | 27 +++++++++++++++++++++++++- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 1 + > 2 files changed, 27 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h > index e7acf118d770..50d05e883dbb 100644 > --- a/arch/x86/include/asm/resctrl.h > +++ b/arch/x86/include/asm/resctrl.h > @@ -36,6 +36,9 @@ DECLARE_PER_CPU(struct resctrl_pqr_state, pqr_state); > DECLARE_STATIC_KEY_FALSE(rdt_enable_key); > DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key); > DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key); > +DECLARE_STATIC_KEY_FALSE(rdt_soft_rmid_enable_key); > + > +void resctrl_mbm_flush_cpu(void); > > /* > * __resctrl_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR > @@ -75,9 +78,31 @@ static inline void __resctrl_sched_in(struct task_struct *tsk) > } > > if (closid != state->cur_closid || rmid != state->cur_rmid) { > + if (static_branch_likely(&rdt_soft_rmid_enable_key)) { Could you please elaborate on the choice of static_branch_likely() (as opposed to static_branch_unlikely())? Reinette
diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h index e7acf118d770..50d05e883dbb 100644 --- a/arch/x86/include/asm/resctrl.h +++ b/arch/x86/include/asm/resctrl.h @@ -36,6 +36,9 @@ DECLARE_PER_CPU(struct resctrl_pqr_state, pqr_state); DECLARE_STATIC_KEY_FALSE(rdt_enable_key); DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key); DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key); +DECLARE_STATIC_KEY_FALSE(rdt_soft_rmid_enable_key); + +void resctrl_mbm_flush_cpu(void); /* * __resctrl_sched_in() - Writes the task's CLOSid/RMID to IA32_PQR_MSR @@ -75,9 +78,31 @@ static inline void __resctrl_sched_in(struct task_struct *tsk) } if (closid != state->cur_closid || rmid != state->cur_rmid) { + if (static_branch_likely(&rdt_soft_rmid_enable_key)) { + /* + * Flush current event counts to outgoing soft rmid + * when it changes. + */ + if (rmid != state->cur_rmid) + resctrl_mbm_flush_cpu(); + + /* + * rmid never changes in this mode, so skip wrmsr if the + * closid is not changing. + */ + if (closid != state->cur_closid) + wrmsr(MSR_IA32_PQR_ASSOC, state->hw_rmid, + closid); + } else { + wrmsr(MSR_IA32_PQR_ASSOC, rmid, closid); + } + + /* + * Record new closid/rmid last so soft rmid case can detect + * changes. + */ state->cur_closid = closid; state->cur_rmid = rmid; - wrmsr(MSR_IA32_PQR_ASSOC, rmid, closid); } } diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index 6ad33f355861..c10f4798156a 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -35,6 +35,7 @@ DEFINE_STATIC_KEY_FALSE(rdt_enable_key); DEFINE_STATIC_KEY_FALSE(rdt_mon_enable_key); DEFINE_STATIC_KEY_FALSE(rdt_alloc_enable_key); +DEFINE_STATIC_KEY_FALSE(rdt_soft_rmid_enable_key); static struct kernfs_root *rdt_root; struct rdtgroup rdtgroup_default; LIST_HEAD(rdt_all_groups);