From: Leo Yan <leo.yan@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
alexander.shishkin@linux.intel.com, Marc Zyngier <maz@kernel.org>,
jolsa@redhat.com, daniel.lezcano@linaro.org,
sboyd@codeaurora.org, linux-kernel@vger.kernel.org,
acme@kernel.org, mingo@redhat.com, john.stultz@linaro.org,
Catalin Marinas <catalin.marinas@arm.com>,
tglx@linutronix.de, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 5/5] arm64: perf: Add cap_user_time_short
Date: Tue, 12 May 2020 22:11:26 +0800 [thread overview]
Message-ID: <20200512141126.GD20352@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <20200512124451.061059334@infradead.org>
On Tue, May 12, 2020 at 02:41:03PM +0200, Peter Zijlstra wrote:
> This completes the ARM64 cap_user_time support.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/arm64/kernel/perf_event.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -1173,6 +1173,7 @@ void arch_perf_update_userpage(struct pe
>
> userpg->cap_user_time = 0;
> userpg->cap_user_time_zero = 0;
> + userpg->cap_user_time_short = 0;
>
> do {
> rd = sched_clock_read_begin(&seq);
> @@ -1183,13 +1184,13 @@ void arch_perf_update_userpage(struct pe
> userpg->time_mult = rd->mult;
> userpg->time_shift = rd->shift;
> userpg->time_zero = rd->epoch_ns;
> + userpg->time_cycle = rd->epoch_cyc;
s/time_cycle/time_cycles, maybe consider to change the naming to
'time_cycle'.
This patch set looks good to me after I tested it on Arm64 board.
Thanks,
Leo
> + userpg->time_mask = rd->sched_clock_mask;
>
> /*
> - * This isn't strictly correct, the ARM64 counter can be
> - * 'short' and then we get funnies when it wraps. The correct
> - * thing would be to extend the perf ABI with a cycle and mask
> - * value, but because wrapping on ARM64 is very rare in
> - * practise this 'works'.
> + * Subtract the cycle base, such that software that
> + * doesn't know about cap_user_time_short still 'works'
> + * assuming no wraps.
> */
> userpg->time_zero -= (rd->epoch_cyc * rd->mult) >> rd->shift;
>
> @@ -1214,4 +1215,5 @@ void arch_perf_update_userpage(struct pe
> */
> userpg->cap_user_time = 1;
> userpg->cap_user_time_zero = 1;
> + userpg->cap_user_time_short = 1;
> }
>
>
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next prev parent reply other threads:[~2020-05-12 14:11 UTC|newest]
Thread overview: 14+ 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 ` [PATCH 1/5] sched_clock: Expose struct clock_read_data Peter Zijlstra
2020-05-12 12:41 ` [PATCH 2/5] arm64: perf: Implement correct cap_user_time Peter Zijlstra
2020-05-12 14:03 ` Leo Yan
2020-05-12 14:08 ` Peter Zijlstra
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 ` [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 14:11 ` Leo Yan [this message]
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 10:11 ` Will Deacon
2020-07-13 12:58 ` Leo Yan
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