From: Shrikanth Hegde <sshegde@linux.ibm.com>
To: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Ben Segall <bsegall@google.com>,
Boqun Feng <boqun.feng@gmail.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Ingo Molnar <mingo@redhat.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Joel Fernandes <joelagnelf@nvidia.com>,
Juri Lelli <juri.lelli@redhat.com>,
Kieran Bingham <kbingham@kernel.org>,
Mel Gorman <mgorman@suse.de>,
Michael Ellerman <mpe@ellerman.id.au>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Nicholas Piggin <npiggin@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Uladzislau Rezki <urezki@gmail.com>,
Valentin Schneider <vschneid@redhat.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Xin Zhao <jackzxcui1989@163.com>,
linux-pm@vger.kernel.org, linux-s390@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle
Date: Thu, 26 Feb 2026 18:27:21 +0530 [thread overview]
Message-ID: <129ebc98-6d1c-42c0-8e60-4072fa82719e@linux.ibm.com> (raw)
In-Reply-To: <1c1e5cf6-5b38-476c-ba49-35510312b064@kernel.org>
Hi Christophe.
>> No. With this patch there will not be any performance difference.
>> All it does is, instead of using mftb uses sched_clock at those places.
>>
>
> For the record, I did some benchmark test with tools/testing/selftests/
> powerpc/benchmarks/null_syscall on powerpc 885 microcontroller:
>
> Without your proposed patch:
>
> root@vgoip:~# ./null_syscall
> 2729.98 ns 360.36 cycles
>
> With your proposed patch below:
>
> root@vgoip:~# ./null_syscall
> 3370.80 ns 444.95 cycles
>
> So as expected it is a huge regression, almost 25% more time to run the
> syscall.
>
> Christophe
>
>
>>
Got it. My bad in assuming it may not happen multiple before vtime_flush.
Btw, can you try latest vtime_reset patch? It shouldn't make any difference.
I tried perf bench syscall basic, and ./null_syscall.
I don't any difference for vtime_reset patch.
next prev parent reply other threads:[~2026-02-26 12:58 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-06 14:22 [PATCH 00/15 v2] tick/sched: Refactor idle cputime accounting Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 01/15] sched/idle: Handle offlining first in idle loop Frederic Weisbecker
2026-02-18 18:22 ` Shrikanth Hegde
2026-02-06 14:22 ` [PATCH 02/15] sched/cputime: Remove superfluous and error prone kcpustat_field() parameter Frederic Weisbecker
2026-02-18 18:25 ` Shrikanth Hegde
2026-02-06 14:22 ` [PATCH 03/15] sched/cputime: Correctly support generic vtime idle time Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle Frederic Weisbecker
2026-02-19 18:30 ` Shrikanth Hegde
2026-02-24 15:41 ` Christophe Leroy (CS GROUP)
2026-02-25 7:46 ` Shrikanth Hegde
2026-02-25 9:45 ` Christophe Leroy (CS GROUP)
2026-02-25 10:34 ` Shrikanth Hegde
2026-02-25 11:14 ` Christophe Leroy (CS GROUP)
2026-02-25 13:33 ` Shrikanth Hegde
2026-02-25 13:54 ` Christophe Leroy (CS GROUP)
2026-02-25 17:47 ` Shrikanth Hegde
2026-02-25 17:59 ` Christophe Leroy (CS GROUP)
2026-02-26 4:06 ` Shrikanth Hegde
2026-02-26 7:32 ` Christophe Leroy (CS GROUP)
2026-02-26 12:57 ` Shrikanth Hegde [this message]
2026-02-06 14:22 ` [PATCH 05/15] s390/time: " Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 06/15] tick/sched: Unify idle cputime accounting Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 07/15] cpufreq: ondemand: Simplify idle cputime granularity test Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 08/15] tick/sched: Remove nohz disabled special case in cputime fetch Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 09/15] tick/sched: Move dyntick-idle cputime accounting to cputime code Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 10/15] tick/sched: Remove unused fields Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 11/15] tick/sched: Account tickless idle cputime only when tick is stopped Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 12/15] tick/sched: Consolidate idle time fetching APIs Frederic Weisbecker
2026-02-06 22:35 ` Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 13/15] sched/cputime: Provide get_cpu_[idle|iowait]_time_us() off-case Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 14/15] sched/cputime: Handle idle irqtime gracefully Frederic Weisbecker
2026-03-03 11:11 ` Shrikanth Hegde
2026-03-20 14:32 ` Frederic Weisbecker
2026-02-06 14:22 ` [PATCH 15/15] sched/cputime: Handle dyntick-idle steal time correctly Frederic Weisbecker
2026-03-03 11:17 ` Shrikanth Hegde
2026-03-24 14:53 ` Frederic Weisbecker
2026-02-11 13:43 ` [PATCH 00/15 v2] tick/sched: Refactor idle cputime accounting Shrikanth Hegde
2026-02-11 17:06 ` Frederic Weisbecker
2026-02-12 7:02 ` Shrikanth Hegde
2026-02-18 18:11 ` Shrikanth Hegde
-- strict thread matches above, loose matches on Subject: below --
2026-01-16 14:51 [PATCH 00/15] " Frederic Weisbecker
2026-01-16 14:51 ` [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle Frederic Weisbecker
2026-02-25 17:53 ` Christophe Leroy (CS GROUP)
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=129ebc98-6d1c-42c0-8e60-4072fa82719e@linux.ibm.com \
--to=sshegde@linux.ibm.com \
--cc=agordeev@linux.ibm.com \
--cc=anna-maria@linutronix.de \
--cc=boqun.feng@gmail.com \
--cc=borntraeger@linux.ibm.com \
--cc=bsegall@google.com \
--cc=chleroy@kernel.org \
--cc=dietmar.eggemann@arm.com \
--cc=frederic@kernel.org \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=jackzxcui1989@163.com \
--cc=jan.kiszka@siemens.com \
--cc=joelagnelf@nvidia.com \
--cc=juri.lelli@redhat.com \
--cc=kbingham@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=maddy@linux.ibm.com \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=neeraj.upadhyay@kernel.org \
--cc=npiggin@gmail.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=rafael@kernel.org \
--cc=rostedt@goodmis.org \
--cc=svens@linux.ibm.com \
--cc=tglx@linutronix.de \
--cc=urezki@gmail.com \
--cc=vincent.guittot@linaro.org \
--cc=viresh.kumar@linaro.org \
--cc=vschneid@redhat.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox