linux-kernel - Re: [tip:sched/core] [sched] 2ae891b826: hackbench.throughput 6.2% regression

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Message-ID: <20250225231014.yztrap5ihain3cd2@airbuntu>
Date: Tue, 25 Feb 2025 23:10:14 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Chen Yu <yu.chen.surf@...mail.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	zihan zhou <15645113830zzh@...il.com>, oe-lkp@...ts.linux.dev,
	kernel test robot <oliver.sang@...el.com>, lkp@...el.com,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	aubrey.li@...ux.intel.com, yu.c.chen@...el.com
Subject: Re: [tip:sched/core] [sched]  2ae891b826:  hackbench.throughput 6.2%
 regression

On 02/25/25 23:35, Chen Yu wrote:
> On 2025-02-25 at 13:42:20 +0000, Qais Yousef wrote:
> > On 02/25/25 21:15, Chen Yu wrote:
> > > On 2025-02-25 at 13:27:05 +0100, Peter Zijlstra wrote:
> > > > On Tue, Feb 25, 2025 at 05:31:34PM +0800, Chen Yu wrote:
> > > > 
> > > > > 
> > > > > But consider that the 6% regression is not that high, and the user might customize
> > > > > base_slice via debugfs on-demand, we can keep an eye on this and revist it in the
> > > > > future(we have encountered some SPECjbb regression due to over-preemption).
> > > > 
> > > > You can specify a per-task slice using sched_attr::sched_runtime. Also
> > > > see commit 857b158dc5e8 ("sched/eevdf: Use sched_attr::sched_runtime to
> > > > set request/slice suggestion")
> > > > 
> > > >
> > > 
> > > Thanks, we'll have a try during the next test cycle.
> > 
> > Could you also try with HRTICK enabled?
> > 
> > 	echo HRTICK | sudo tee /sys/kernel/debug/sched/features
> 
> Sure. Is HRTICK supposed to encourage preemption? I thought
> hackbench might be sensitive to preemption(downgrading).

Yes my bad, I don't know why I read this as preemption was happening later not
earlier. Please ignore me then.

Thanks

--
Qais Yousef