From: Valentin Schneider <vschneid@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: bigeasy@linutronix.de, mark.rutland@arm.com, maz@kernel.org,
catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org,
kernel@xen0n.name, hca@linux.ibm.com, gor@linux.ibm.com,
agordeev@linux.ibm.com, borntraeger@linux.ibm.com,
svens@linux.ibm.com, pbonzini@redhat.com, wanpengli@tencent.com,
vkuznets@redhat.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, jgross@suse.com, boris.ostrovsky@oracle.com,
daniel.lezcano@linaro.org, kys@microsoft.com,
haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
rafael@kernel.org, longman@redhat.com, boqun.feng@gmail.com,
pmladek@suse.com, senozhatsky@chromium.org, rostedt@goodmis.org,
john.ogness@linutronix.de, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
jstultz@google.com, sboyd@kernel.org,
linux-kernel@vger.kernel.org, loongarch@lists.linux.dev,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
linux-hyperv@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH v2 04/13] arm64/arch_timer: Provide noinstr sched_clock_read() functions
Date: Wed, 07 Jun 2023 09:58:22 +0100 [thread overview]
Message-ID: <xhsmhsfb3odht.mognet@vschneid.remote.csb> (raw)
In-Reply-To: <20230602115451.GG620383@hirez.programming.kicks-ass.net>
On 02/06/23 13:54, Peter Zijlstra wrote:
> On Wed, May 24, 2023 at 05:40:47PM +0100, Valentin Schneider wrote:
>>
>> So this bit sent me on a little spelunking session :-)
>>
>> From a control flow perspective the initialization isn't required, but then
>> I looked into the comment and found it comes from the
>> arch_timer_read_counter() definition... Which itself doesn't get used by
>> sched_clock() until the sched_clock_register() below!
>>
>> So AFAICT that comment was true as of
>>
>> 220069945b29 ("clocksource: arch_timer: Add support for memory mapped timers")
>>
>> but not after a commit that came 2 months later:
>>
>> 65cd4f6c99c1 ("arch_timer: Move to generic sched_clock framework")
>>
>> which IIUC made arm/arm64 follow the default approach of using the
>> jiffy-based sched_clock() before probing DT/ACPI and registering a "proper"
>> sched_clock.
>>
>> All of that to say: the comment about arch_timer_read_counter() vs early
>> sched_clock() doesn't apply anymore, but I think we need to keep its
>> initalization around for stuff like get_cycles(). This initialization here
>> should be OK to put to the bin, though.
>
> Something like the below folded in then?
>
Much better, thank you!
next prev parent reply other threads:[~2023-06-07 9:01 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-19 10:20 [PATCH v2 00/13] local_clock() vs noinstr Peter Zijlstra
2023-05-19 10:20 ` [PATCH v2 01/13] seqlock/latch: Provide raw_read_seqcount_latch_retry() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 02/13] time/sched_clock: Provide sched_clock_noinstr() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 03/13] arm64/io: Always inline all of __raw_{read,write}[bwlq]() Peter Zijlstra
2023-05-24 16:40 ` Valentin Schneider
2023-05-19 10:21 ` [PATCH v2 04/13] arm64/arch_timer: Provide noinstr sched_clock_read() functions Peter Zijlstra
2023-05-24 16:40 ` Valentin Schneider
2023-06-02 11:54 ` Peter Zijlstra
2023-06-07 8:58 ` Valentin Schneider [this message]
2023-05-19 10:21 ` [PATCH v2 05/13] loongarch: Provide noinstr sched_clock_read() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 06/13] s390/time: Provide sched_clock_noinstr() Peter Zijlstra
2023-05-22 14:18 ` Heiko Carstens
2023-05-19 10:21 ` [PATCH v2 07/13] math64: Always inline u128 version of mul_u64_u64_shr() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 08/13] x86/vdso: Fix gettimeofday masking Peter Zijlstra
2023-05-31 15:27 ` Thomas Gleixner
2023-05-31 22:46 ` Thomas Gleixner
2023-05-31 22:46 ` Thomas Gleixner
2023-05-19 10:21 ` [PATCH v2 09/13] clocksource: hyper-v: Adjust hv_read_tsc_page_tsc() to avoid special casing U64_MAX Peter Zijlstra
2023-05-19 18:38 ` Michael Kelley (LINUX)
2023-05-19 10:21 ` [PATCH v2 10/13] clocksource: hyper-v: Provide noinstr sched_clock() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 11/13] x86/tsc: Provide sched_clock_noinstr() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 12/13] sched/clock: Provide local_clock_noinstr() Peter Zijlstra
2023-05-19 10:21 ` [PATCH v2 13/13] cpuidle: Use local_clock_noinstr() Peter Zijlstra
2023-05-19 14:13 ` Rafael J. Wysocki
2023-05-19 18:48 ` [PATCH v2 00/13] local_clock() vs noinstr Michael Kelley (LINUX)
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