From nobody Tue Apr 7 01:33:44 2026 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 830FA364925; Tue, 17 Mar 2026 10:47:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773744469; cv=none; b=M/74pH3YEMpRnYKQnVHARQcOraJr4VZwkQGkumdgmnAZm2BIGVdLvgpb+QW2AIgnzxc2HyDDVcrpGMLuTKu/ULS8q8M19fg21ZRsJPimuKu+i2VndwzUs98J4h85ZoKP67GZjUXX6bonkh95PfpPDq1SRaAG07efJbt7LC0MCK4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773744469; c=relaxed/simple; bh=BGCul55Vi9g6OEb/YK/4n28IrjDLTj1cMq11HW01sMA=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=GnyrU89YiX51HA7Y0fi07RHjHH6Nqj2gSPoXP3bD5+oJIorzBdENqlIq9dfY5YkpTRdWlQL8nWhz5jvhe2ZbI6kQS+PjA8/YZmzir7uWHuRjn5oQKkZbYE1L1ZmQ7WbZ00gq+qLHjj+8fUY+Xv1j+H4YHi6CFaGyA2j/no+VpvM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=bECMsyEM; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bECMsyEM" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=1uNe0XdInvRjclNE9H5+/v0jGlGWKmLTRIC+ImkMMgE=; b=bECMsyEMEcS35UkOR0CvcVT6Jm OG/caR4uU65ZsfZopdqAp6ocB44xslaF8rE9D+xhPqP5iOYtyob2YE0bn4b85YeY3xsXxsiRkEfVw ysSXVk3bss3jzlYShCzg4NEogniQNNUBvZPGVJjz6GL7mE+Y4Ie/RUNX2UMvZeHaKgm8YfALOvjrr yNceYQsCpgk7cp3j7lendqD6JtRzYh5R1yUvFum0YGB5c3vdio4T7YplzwSu8HghUjJuc4Gyub/LK Cfv/qoGFXVzliTKyjvZIJb2BwADo0fFCvGLW4iXksTQcU+3sXCRV9X5QH6GZoM0PToObzEbLj1AAr ol0ccsmQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1w2RxY-00000002YWq-0siI; Tue, 17 Mar 2026 10:47:36 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id 21A083032BC; Tue, 17 Mar 2026 11:47:35 +0100 (CET) Message-ID: <20260317104342.700967988@infradead.org> User-Agent: quilt/0.68 Date: Tue, 17 Mar 2026 10:51:16 +0100 From: Peter Zijlstra To: mingo@kernel.org Cc: longman@redhat.com, chenridong@huaweicloud.com, peterz@infradead.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, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jstultz@google.com, kprateek.nayak@amd.com Subject: [RFC][PATCH 3/8] sched/fair: Add cgroup_mode: UP References: <20260317095113.387450089@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Instead of calculating the proportional fraction of tg->shares for each CPU, just give each CPU the full measure, ignoring these pesky SMP problems. Signed-off-by: Peter Zijlstra (Intel) --- kernel/sched/debug.c | 3 ++- kernel/sched/fair.c | 19 ++++++++++++++++++- 2 files changed, 20 insertions(+), 2 deletions(-) --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -588,9 +588,10 @@ static void debugfs_fair_server_init(voi } =20 #ifdef CONFIG_FAIR_GROUP_SCHED -int cgroup_mode =3D 0; +int cgroup_mode =3D 1; =20 static const char *cgroup_mode_str[] =3D { + "up", "smp", }; =20 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4152,7 +4152,7 @@ static inline int throttled_hierarchy(st * * hence icky! */ -static long calc_group_shares(struct cfs_rq *cfs_rq) +static long calc_smp_shares(struct cfs_rq *cfs_rq) { long tg_weight, tg_shares, load, shares; struct task_group *tg =3D cfs_rq->tg; @@ -4187,6 +4187,23 @@ static long calc_group_shares(struct cfs } =20 /* + * Ignore this pesky SMP stuff, use (4). + */ +static long calc_up_shares(struct cfs_rq *cfs_rq) +{ + struct task_group *tg =3D cfs_rq->tg; + return READ_ONCE(tg->shares); +} + +static long calc_group_shares(struct cfs_rq *cfs_rq) +{ + if (cgroup_mode =3D=3D 0) + return calc_up_shares(cfs_rq); + + return calc_smp_shares(cfs_rq); +} + +/* * Recomputes the group entity based on the current state of its group * runqueue. */