From: Leo Yan <leo.yan@linaro.org> To: Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>, Thomas Gleixner <tglx@linutronix.de>, Paul Cercueil <paul@crapouillou.net>, "Ben Dooks (Codethink)" <ben.dooks@codethink.co.uk>, "Ahmed S. Darwish" <a.darwish@linutronix.de>, Adrian Hunter <adrian.hunter@intel.com>, Kan Liang <kan.liang@linux.intel.com>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/6] perf: Add perf_event_mmap_page::cap_user_time_short ABI Date: Wed, 15 Jul 2020 10:05:10 +0800 Message-ID: <20200715020512.20991-5-leo.yan@linaro.org> (raw) In-Reply-To: <20200715020512.20991-1-leo.yan@linaro.org> From: Peter Zijlstra <peterz@infradead.org> In order to support short clock counters, provide an ABI extension. 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(-) diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 7b2d6fc9e6ed..21a1edd08cbe 100644 --- 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. -- 2.17.1
next prev parent reply index Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-15 2:05 [PATCH v2 0/6] arm64: perf: Proper cap_user_time* support Leo Yan 2020-07-15 2:05 ` [PATCH v2 1/6] sched_clock: Expose struct clock_read_data Leo Yan 2020-07-15 5:56 ` Ahmed S. Darwish 2020-07-15 6:54 ` Leo Yan 2020-07-15 7:21 ` Ahmed S. Darwish 2020-07-15 8:12 ` Peter Zijlstra 2020-07-15 8:14 ` peterz 2020-07-15 9:23 ` Ahmed S. Darwish 2020-07-15 9:52 ` Peter Zijlstra 2020-07-15 11:59 ` [PATCH] time/sched_clock: Use raw_read_seqcount_latch() Ahmed S. Darwish 2020-07-15 15:29 ` Leo Yan 2020-07-15 15:58 ` Peter Zijlstra 2020-07-16 5:22 ` Leo Yan 2020-09-10 15:08 ` [tip: locking/core] time/sched_clock: Use raw_read_seqcount_latch() during suspend tip-bot2 for Ahmed S. Darwish 2020-07-15 2:05 ` [PATCH v2 2/6] arm64: perf: Implement correct cap_user_time Leo Yan 2020-07-15 8:38 ` Peter Zijlstra 2020-07-15 15:39 ` Leo Yan 2020-07-15 2:05 ` [PATCH v2 3/6] arm64: perf: Only advertise cap_user_time for arch_timer Leo Yan 2020-07-15 2:05 ` Leo Yan [this message] 2020-07-15 2:05 ` [PATCH v2 5/6] arm64: perf: Add cap_user_time_short Leo Yan 2020-07-15 2:05 ` [PATCH v2 6/6] tools headers UAPI: Update tools's copy of linux/perf_event.h Leo Yan 2020-07-15 5:17 ` [PATCH v2 0/6] arm64: perf: Proper cap_user_time* support Ahmed S. Darwish 2020-07-15 6:29 ` Leo Yan
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20200715020512.20991-5-leo.yan@linaro.org \ --to=leo.yan@linaro.org \ --cc=a.darwish@linutronix.de \ --cc=acme@kernel.org \ --cc=adrian.hunter@intel.com \ --cc=alexander.shishkin@linux.intel.com \ --cc=ben.dooks@codethink.co.uk \ --cc=catalin.marinas@arm.com \ --cc=jolsa@redhat.com \ --cc=kan.liang@linux.intel.com \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kernel@vger.kernel.org \ --cc=mark.rutland@arm.com \ --cc=mingo@redhat.com \ --cc=namhyung@kernel.org \ --cc=paul@crapouillou.net \ --cc=peterz@infradead.org \ --cc=tglx@linutronix.de \ --cc=will@kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
LKML Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lkml.kernel.org/lkml/0 lkml/git/0.git git clone --mirror https://lkml.kernel.org/lkml/1 lkml/git/1.git git clone --mirror https://lkml.kernel.org/lkml/2 lkml/git/2.git git clone --mirror https://lkml.kernel.org/lkml/3 lkml/git/3.git git clone --mirror https://lkml.kernel.org/lkml/4 lkml/git/4.git git clone --mirror https://lkml.kernel.org/lkml/5 lkml/git/5.git git clone --mirror https://lkml.kernel.org/lkml/6 lkml/git/6.git git clone --mirror https://lkml.kernel.org/lkml/7 lkml/git/7.git git clone --mirror https://lkml.kernel.org/lkml/8 lkml/git/8.git git clone --mirror https://lkml.kernel.org/lkml/9 lkml/git/9.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 lkml lkml/ https://lkml.kernel.org/lkml \ linux-kernel@vger.kernel.org public-inbox-index lkml Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel AGPL code for this site: git clone https://public-inbox.org/public-inbox.git