Messages in this thread | | | From | "liwei (GF)" <> | Subject | Re: [PATCH v2 1/4] perf tools: Support Arm arch timer counter | Date | Thu, 20 Aug 2020 10:56:46 +0800 |
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Hi Leo
On 2020/8/7 15:16, Leo Yan wrote: > The Arm arch timer can be used to calculate timestamp, the basic idea is > the arch timer's counter value can be recorded in the hardware tracing > data, e.g. the arch timer's counter value can be used for Arm CoreSight > (not now but might be implemented later) and Arm SPE. So we need a way > to convert the arch timer's counter to the system time, the conversion > is dependent on some related parameters, e.g. 'time_shift', 'time_mult', > 'time_offset', etc; furthermore, to handle the counter wrapping issue, > perf tool needs to know 'time_cycles' and 'time_mask' for correction. > > This patch is to support Arm arch timer by reading out the relevant > parameters from the head of first mmaped page. And these parameters > will be stored into the structure 'perf_arch_timer_conversion' for > later calculation timestamp. > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > tools/perf/arch/arm64/util/Build | 1 + > tools/perf/arch/arm64/util/arch_timer.c | 50 +++++++++++++++++++++++++ > tools/perf/util/arm_arch_timer.h | 20 ++++++++++ > 3 files changed, 71 insertions(+) > create mode 100644 tools/perf/arch/arm64/util/arch_timer.c > create mode 100644 tools/perf/util/arm_arch_timer.h > > diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build > index 5c13438c7bd4..77f4d7b30932 100644 > --- a/tools/perf/arch/arm64/util/Build > +++ b/tools/perf/arch/arm64/util/Build > @@ -1,3 +1,4 @@ > +perf-y += arch_timer.o > perf-y += header.o > perf-y += machine.o > perf-y += perf_regs.o > diff --git a/tools/perf/arch/arm64/util/arch_timer.c b/tools/perf/arch/arm64/util/arch_timer.c > new file mode 100644 > index 000000000000..dcc217c294fc > --- /dev/null > +++ b/tools/perf/arch/arm64/util/arch_timer.c > @@ -0,0 +1,50 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <stdbool.h> > +#include <errno.h> > + > +#include <linux/stddef.h> > +#include <linux/perf_event.h> > + > +#include <linux/types.h> > +#include <asm/barrier.h> > +#include "../../../util/debug.h" > +#include "../../../util/event.h" > +#include "../../../util/synthetic-events.h" > +#include "../../../util/arm_arch_timer.h" > + > +int perf_read_arch_timer_conversion(const struct perf_event_mmap_page *pc, > + struct perf_arch_timer_conversion *tc) > +{ > + bool cap_user_time_zero, cap_user_time_short; > + u32 seq; > + int i = 0; > + > + while (1) { > + seq = pc->lock; > + /* Add barrier between the sequence lock and data accessing */ > + rmb(); > + > + tc->time_mult = pc->time_mult; > + tc->time_shift = pc->time_shift; > + tc->time_zero = pc->time_zero; > + tc->time_cycles = pc->time_cycles; > + tc->time_mask = pc->time_mask; > + cap_user_time_zero = pc->cap_user_time_zero; > + cap_user_time_short = pc->cap_user_time_short; > + > + /* Add barrier between the data accessing and sequence lock */ > + rmb(); > + if (pc->lock == seq && !(seq & 1)) > + break; > + if (++i > 10000) { > + pr_debug("%s: failed to get perf_event_mmap_page lock\n", > + __func__); > + return -EINVAL; > + } > + } > + > + if (!cap_user_time_zero || !cap_user_time_short) > + return -EOPNOTSUPP; > + > + return 0; > +}
Should we implement the perf_event__synth_time_conv() method? As it can be supported on arm64 arch now.
These is also a tsc get method called rdtsc(), weak implementation in 'tools/perf/util/tsc.c', maybe we should rename it to an arch independent name, and implement the arm64 version (read_cntvct_el0 in patch 3) here. Thus we can also make the testcase generic, instead of adding a new one for arm64 :).
Thanks, Wei
> diff --git a/tools/perf/util/arm_arch_timer.h b/tools/perf/util/arm_arch_timer.h > new file mode 100644 > index 000000000000..a3263cc4e5cf > --- /dev/null > +++ b/tools/perf/util/arm_arch_timer.h > @@ -0,0 +1,20 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __PERF_ARM_ARCH_TIMER_H > +#define __PERF_ARM_ARCH_TIMER_H > + > +#include <linux/types.h> > + > +struct perf_arch_timer_conversion { > + u16 time_shift; > + u32 time_mult; > + u64 time_zero; > + u64 time_cycles; > + u64 time_mask; > +}; > + > +struct perf_event_mmap_page; > + > +int perf_read_arch_timer_conversion(const struct perf_event_mmap_page *pc, > + struct perf_arch_timer_conversion *tc); > + > +#endif // __PERF_ARM_ARCH_TIMER_H >
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