From: Peter Zijlstra <peterz@infradead.org> To: Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Leo Yan <leo.yan@linaro.org> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, daniel.lezcano@linaro.org, tglx@linutronix.de, sboyd@codeaurora.org, john.stultz@linaro.org, "Peter Zijlstra (Intel)" <peterz@infradead.org> Subject: [PATCH 4/5] perf: Add perf_event_mmap_page::cap_user_time_short ABI Date: Tue, 12 May 2020 14:41:02 +0200 [thread overview] Message-ID: <20200512124450.981890259@infradead.org> (raw) In-Reply-To: 20200512124058.833263033@infradead.org In order to support short clock counters, provide an ABI extention. As a whole: u64 time, delta, cyc = read_cycle_counter(); + if (cap_user_time_short) + cyc = time_cycle + ((cyc - time_cycle) & time_mask); delta = mul_u64_u32_shr(cyc, time_mult, time_shift); if (cap_user_time_zero) time = time_zero + delta; delta += time_offset; Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- include/uapi/linux/perf_event.h | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -532,9 +532,10 @@ struct perf_event_mmap_page { cap_bit0_is_deprecated : 1, /* Always 1, signals that bit 0 is zero */ cap_user_rdpmc : 1, /* The RDPMC instruction can be used to read counts */ - cap_user_time : 1, /* The time_* fields are used */ + cap_user_time : 1, /* The time_{shift,mult,offset} fields are used */ cap_user_time_zero : 1, /* The time_zero field is used */ - cap_____res : 59; + cap_user_time_short : 1, /* the time_{cycle,mask} fields are used */ + cap_____res : 58; }; }; @@ -593,13 +594,29 @@ struct perf_event_mmap_page { * ((rem * time_mult) >> time_shift); */ __u64 time_zero; + __u32 size; /* Header size up to __reserved[] fields. */ + __u32 __reserved_1; + + /* + * If cap_usr_time_short, the hardware clock is less than 64bit wide + * and we must compute the 'cyc' value, as used by cap_usr_time, as: + * + * cyc = time_cycles + ((cyc - time_cycles) & time_mask) + * + * NOTE: this form is explicitly chosen such that cap_usr_time_short + * is a correction on top of cap_usr_time, and code that doesn't + * know about cap_usr_time_short still works under the assumption + * the counter doesn't wrap. + */ + __u64 time_cycles; + __u64 time_mask; /* * Hole for extension of the self monitor capabilities */ - __u8 __reserved[118*8+4]; /* align to 1k. */ + __u8 __reserved[116*8]; /* align to 1k. */ /* * Control data for the mmap() data buffer.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org> To: Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Leo Yan <leo.yan@linaro.org> Cc: alexander.shishkin@linux.intel.com, daniel.lezcano@linaro.org, sboyd@codeaurora.org, linux-kernel@vger.kernel.org, acme@kernel.org, "Peter Zijlstra \(Intel\)" <peterz@infradead.org>, mingo@redhat.com, john.stultz@linaro.org, tglx@linutronix.de, jolsa@redhat.com, linux-arm-kernel@lists.infradead.org Subject: [PATCH 4/5] perf: Add perf_event_mmap_page::cap_user_time_short ABI Date: Tue, 12 May 2020 14:41:02 +0200 [thread overview] Message-ID: <20200512124450.981890259@infradead.org> (raw) In-Reply-To: 20200512124058.833263033@infradead.org In order to support short clock counters, provide an ABI extention. As a whole: u64 time, delta, cyc = read_cycle_counter(); + if (cap_user_time_short) + cyc = time_cycle + ((cyc - time_cycle) & time_mask); delta = mul_u64_u32_shr(cyc, time_mult, time_shift); if (cap_user_time_zero) time = time_zero + delta; delta += time_offset; Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- include/uapi/linux/perf_event.h | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -532,9 +532,10 @@ struct perf_event_mmap_page { cap_bit0_is_deprecated : 1, /* Always 1, signals that bit 0 is zero */ cap_user_rdpmc : 1, /* The RDPMC instruction can be used to read counts */ - cap_user_time : 1, /* The time_* fields are used */ + cap_user_time : 1, /* The time_{shift,mult,offset} fields are used */ cap_user_time_zero : 1, /* The time_zero field is used */ - cap_____res : 59; + cap_user_time_short : 1, /* the time_{cycle,mask} fields are used */ + cap_____res : 58; }; }; @@ -593,13 +594,29 @@ struct perf_event_mmap_page { * ((rem * time_mult) >> time_shift); */ __u64 time_zero; + __u32 size; /* Header size up to __reserved[] fields. */ + __u32 __reserved_1; + + /* + * If cap_usr_time_short, the hardware clock is less than 64bit wide + * and we must compute the 'cyc' value, as used by cap_usr_time, as: + * + * cyc = time_cycles + ((cyc - time_cycles) & time_mask) + * + * NOTE: this form is explicitly chosen such that cap_usr_time_short + * is a correction on top of cap_usr_time, and code that doesn't + * know about cap_usr_time_short still works under the assumption + * the counter doesn't wrap. + */ + __u64 time_cycles; + __u64 time_mask; /* * Hole for extension of the self monitor capabilities */ - __u8 __reserved[118*8+4]; /* align to 1k. */ + __u8 __reserved[116*8]; /* align to 1k. */ /* * Control data for the mmap() data buffer. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-05-12 12:47 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-12 12:40 [PATCH 0/5] arm64: perf: Proper cap_user_time* support Peter Zijlstra 2020-05-12 12:40 ` Peter Zijlstra 2020-05-12 12:40 ` [PATCH 1/5] sched_clock: Expose struct clock_read_data Peter Zijlstra 2020-05-12 12:40 ` Peter Zijlstra 2020-05-12 12:41 ` [PATCH 2/5] arm64: perf: Implement correct cap_user_time Peter Zijlstra 2020-05-12 12:41 ` Peter Zijlstra 2020-05-12 14:03 ` Leo Yan 2020-05-12 14:03 ` Leo Yan 2020-05-12 14:08 ` Peter Zijlstra 2020-05-12 14:08 ` Peter Zijlstra 2020-05-12 16:05 ` kbuild test robot 2020-05-12 16:05 ` kbuild test robot 2020-05-12 16:05 ` kbuild test robot 2020-05-12 12:41 ` [PATCH 3/5] arm64: perf: Only advertise cap_user_time for arch_timer Peter Zijlstra 2020-05-12 12:41 ` Peter Zijlstra 2020-05-12 12:41 ` Peter Zijlstra [this message] 2020-05-12 12:41 ` [PATCH 4/5] perf: Add perf_event_mmap_page::cap_user_time_short ABI Peter Zijlstra 2020-05-12 12:41 ` [PATCH 5/5] arm64: perf: Add cap_user_time_short Peter Zijlstra 2020-05-12 12:41 ` Peter Zijlstra 2020-05-12 14:11 ` Leo Yan 2020-05-12 14:11 ` Leo Yan 2020-05-12 16:59 ` kbuild test robot 2020-05-12 16:59 ` kbuild test robot 2020-05-12 16:59 ` kbuild test robot 2020-07-13 6:08 ` [PATCH 0/5] arm64: perf: Proper cap_user_time* support Leo Yan 2020-07-13 6:08 ` Leo Yan 2020-07-13 10:11 ` Will Deacon 2020-07-13 10:11 ` Will Deacon 2020-07-13 12:58 ` Leo Yan 2020-07-13 12:58 ` Leo Yan
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