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perf/x86/intel: Save/restore LBR stack during context switch 

When the LBR call stack is enabled, it is necessary to save/restore
the LBR stack on context switch. The solution is saving/restoring
the LBR stack to/from task's perf event context.

The LBR stack is saved/restored only when there are events that use
the LBR call stack. If no event uses LBR call stack, the LBR stack
is reset when task is scheduled in.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-10-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yan, Zheng 2014-11-04 21:56:05 -05:00 committed by Ingo Molnar
parent 63f0c1d841
commit 76cb2c617f
1 changed files with 76 additions and 12 deletions
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88
arch/x86/kernel/cpu/perf_event_intel_lbr.c
View File

@ -180,13 +180,89 @@ void intel_pmu_lbr_reset(void)
intel_pmu_lbr_reset_64();
}
/*
* TOS = most recently recorded branch
*/
static inline u64 intel_pmu_lbr_tos(void)
{
u64 tos;
rdmsrl(x86_pmu.lbr_tos, tos);
return tos;
}
enum {
LBR_NONE,
LBR_VALID,
};
static void __intel_pmu_lbr_restore(struct x86_perf_task_context *task_ctx)
{
int i;
unsigned lbr_idx, mask;
u64 tos;
if (task_ctx->lbr_callstack_users == 0 ||
task_ctx->lbr_stack_state == LBR_NONE) {
intel_pmu_lbr_reset();
return;
}
mask = x86_pmu.lbr_nr - 1;
tos = intel_pmu_lbr_tos();
for (i = 0; i < x86_pmu.lbr_nr; i++) {
lbr_idx = (tos - i) & mask;
wrmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
wrmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
}
task_ctx->lbr_stack_state = LBR_NONE;
}
static void __intel_pmu_lbr_save(struct x86_perf_task_context *task_ctx)
{
int i;
unsigned lbr_idx, mask;
u64 tos;
if (task_ctx->lbr_callstack_users == 0) {
task_ctx->lbr_stack_state = LBR_NONE;
return;
}
mask = x86_pmu.lbr_nr - 1;
tos = intel_pmu_lbr_tos();
for (i = 0; i < x86_pmu.lbr_nr; i++) {
lbr_idx = (tos - i) & mask;
rdmsrl(x86_pmu.lbr_from + lbr_idx, task_ctx->lbr_from[i]);
rdmsrl(x86_pmu.lbr_to + lbr_idx, task_ctx->lbr_to[i]);
}
task_ctx->lbr_stack_state = LBR_VALID;
}
void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
struct x86_perf_task_context *task_ctx;
if (!x86_pmu.lbr_nr)
return;
/*
* If LBR callstack feature is enabled and the stack was saved when
* the task was scheduled out, restore the stack. Otherwise flush
* the LBR stack.
*/
task_ctx = ctx ? ctx->task_ctx_data : NULL;
if (task_ctx) {
if (sched_in) {
__intel_pmu_lbr_restore(task_ctx);
cpuc->lbr_context = ctx;
} else {
__intel_pmu_lbr_save(task_ctx);
}
return;
}
/*
* When sampling the branck stack in system-wide, it may be
* necessary to flush the stack on context switch. This happens
@ -279,18 +355,6 @@ void intel_pmu_lbr_disable_all(void)
__intel_pmu_lbr_disable();
}
/*
* TOS = most recently recorded branch
*/
static inline u64 intel_pmu_lbr_tos(void)
{
u64 tos;
rdmsrl(x86_pmu.lbr_tos, tos);
return tos;
}
static void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)
{
unsigned long mask = x86_pmu.lbr_nr - 1;