From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03C291DFD1 for ; Tue, 8 Oct 2024 15:07:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728400049; cv=none; b=OO1oyKjYTTUk1ruhg6vtvjmThrPrsxMOck2LbW0VJ8h8Itd0kkTrg2KVAa5mbXXLaSjnaNQmzv+tJoMT15FKBW41OV3DSs5EkI0EgRKfKbLyP5dIHcoAUoh55/MSCxTiI4SRsEudvA8CyICIcjigL3JHBgGbOKiGHPkdaGAH2JM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728400049; c=relaxed/simple; bh=QCgviBaJeMoGo2qmUaA/6pGtkNj7nqyUSHHv20Utdrw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=o0Nyfz6/+DuL5GxgsDY0h8qLnwHlaF3LlYMD/7MEgIBRR5ZBYL0qCJfc01x1SvXpESzIp0qRnrFVoKDrQB62iWFqWZ7s7vuPR7396VTzvvSrhMg5R0k2Ti7VBK9N2JnU4wWYcFp0Migroj/gnued1nmJ5S1LvWyOWmGFYwVPFss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=HvRP+z0O; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=YJfttHoR; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="HvRP+z0O"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="YJfttHoR" Date: Tue, 8 Oct 2024 17:07:24 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1728400046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VPc3xG3krSZmBTcw/AubqHB8oaYBJUxW3tDmqN3SWB4=; b=HvRP+z0Oai1Hm6fWBEzOmbK0AnFUxvRqQ1fKyjVqFZwpcYHa1rLkbOADyL7TYVkl+vzJ7A qwTQwxY5FHHg9bAoHdkhm9TZEg4FP7KScxwDxOubi9iKtQqabUCTPPwyyB7adjGuDzf0b0 jCFjvvijGFBSPKmCug8R4gG2gMPDeOez0Hryeuck2/2uBsi2LLHRINPWXZhpr49XIoTxOS V10g3IUX5PXo5L54h73EqZq0FNncwODOO0DEnxg/RupvH4GZTrQbErx3S5F8HDC3IxbIjJ ZQoEf7NwechzhgRD2lhZALXIPo+aa/X9YXuSEz7l/fJax/MYpZ1nHA1UXbfbgg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1728400046; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VPc3xG3krSZmBTcw/AubqHB8oaYBJUxW3tDmqN3SWB4=; b=YJfttHoRwDElmtwGqAzKc+QiXD1hXeeHwKbOhp1CuFlsPjYvXcs9WzanlvTSPEcbw4cbqn 3FzWBIRfn8U3aaDQ== From: Sebastian Andrzej Siewior To: Peter Zijlstra 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 5/5] sched: Add laziest preempt model Message-ID: <20241008150724.s5rOW5nS@linutronix.de> References: <20241007074609.447006177@infradead.org> <20241007075055.671722644@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20241007075055.671722644@infradead.org> On 2024-10-07 09:46:14 [+0200], Peter Zijlstra wrote: > Much like LAZY, except lazier still. It will not promote LAZY to full > preempt on tick and compete with None for suckage. >=20 > (do we really wants this?) This is like NONE/ VOLUNTARY without the .*_resched(). irqentry_exit_cond_resched() and preempt_schedule.*() does nothing because only the lazy bit is set. This should trigger all the spots which were filled with cond_resched() to avoid warnings, right? There is nothing that will force a preemption, right? > Signed-off-by: Peter Zijlstra (Intel) =E2=80=A6 The description is the same for two lazy models. > +config PREEMPT_LAZIEST > + bool "Scheduler controlled preemption model" bool "Scheduler controlled preemption model (relaxed)" > + depends on !ARCH_NO_PREEMPT > + depends on ARCH_HAS_PREEMPT_LAZY > + select PREEMPT_BUILD if !PREEMPT_DYNAMIC > + help > + This option provides a scheduler driven preemption model that > + is fundamentally similar to full preemption, but is least > + eager to preempt SCHED_NORMAL tasks in an attempt to > + reduce lock holder preemption and recover some of the performance > + gains seen from using no preemption. The scheduler won't force the task off-CPU if the task does not give up voluntary. > + > endchoice Sebastian