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From: Frederic Weisbecker <frederic@kernel.org>
To: Oliver Sang <oliver.sang@intel.com>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>,
	oe-lkp@lists.linux.dev, lkp@intel.com,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com
Subject: Re: [tip:timers/core] [timers]  7ee9887703:  netperf.Throughput_Mbps -1.2% regression
Date: Tue, 5 Mar 2024 12:35:30 +0100	[thread overview]
Message-ID: <ZecDghwFnq0Tmngo@lothringen> (raw)
In-Reply-To: <ZeaAx662HfbpMLdg@xsang-OptiPlex-9020>

On Tue, Mar 05, 2024 at 10:17:43AM +0800, Oliver Sang wrote:
>      20.97 ±  3%      -9.7       11.23 ± 16%      -9.6       11.40 ±  4%  perf-profile.calltrace.cycles-pp.__napi_poll.net_rx_action.__do_softirq.irq_exit_rcu.sysvec_apic_timer_interrupt

And yes, fewer time spent in IRQ-tail softirq processing.

>       1.70 ± 13%      +5.6        7.28 ± 14%      +5.8        7.54 ± 15%  perf-profile.calltrace.cycles-pp.__napi_poll.net_rx_action.__do_softirq.run_ksoftirqd.smpboot_thread_fn

And more time spent in ksoftirqd softirq processing.

This can match the increase in involuntary context switches: IRQ-tail softirq
processing takes too much time, possibly due to long lasting remote timer
expiring, ksoftirqd is then scheduled, preempting netperf (through
might_resched()/cond_resched()) as this is a voluntary preemption kernel).

Thanks.

  parent reply	other threads:[~2024-03-05 11:35 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-01  8:09 [tip:timers/core] [timers] 7ee9887703: netperf.Throughput_Mbps -1.2% regression kernel test robot
2024-03-04  0:32 ` Frederic Weisbecker
2024-03-04  2:13   ` Oliver Sang
2024-03-04 11:28     ` Frederic Weisbecker
2024-03-05  2:17       ` Oliver Sang
2024-03-05 10:46         ` Frederic Weisbecker
2024-03-05 11:21         ` Frederic Weisbecker
2024-03-05 11:35         ` Frederic Weisbecker [this message]
2024-03-12 23:57 ` Frederic Weisbecker
2024-03-13  8:25   ` Thomas Gleixner

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