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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, mingo@kernel.org, linux-kernel@vger.kernel.org,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
	mgorman@suse.de, vschneid@redhat.com, ankur.a.arora@oracle.com,
	efault@gmx.de
Subject: Re: [PATCH 0/5] sched: Lazy preemption muck
Message-ID: <20241008153232.YwZfzF0r@linutronix.de>
References: <20241007074609.447006177@infradead.org>
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In-Reply-To: <20241007074609.447006177@infradead.org>

On 2024-10-07 09:46:09 [+0200], Peter Zijlstra wrote:
> Hi!
>=20
> During LPC Thomas reminded me that the lazy preemption stuff was not ther=
e yet.
>=20
> So here goes, robot says it builds, and I checked both a regular and PREE=
MPT_RT
> build boots and can change the mode.
>=20
> Please have a poke.

While comparing this vs what I have:
- need_resched()
  It checked both (tif_need_resched_lazy() || tif_need_resched()) while
  now it only looks at tif_need_resched().
  Also ensured that raw_irqentry_exit_cond_resched() does not trigger on
  lazy.=20
  I guess you can argue both ways what makes sense, just noting=E2=80=A6

- __account_cfs_rq_runtime() and hrtick_start_fair()
  Both have a resched_curr() instead of resched_curr_lazy(). Is this on
  purpose?

This is actually the main difference (ignoring the moving the RT bits
and dynamic-sched). The lazy-resched is slightly different but it should
do the same thing.
I have also tracing and riscv bits which I port tomorrow, test and add
to your pile.

Sebastian