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 097361632F2 for ; Thu, 14 Nov 2024 09:16:17 +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=1731575781; cv=none; b=roSfxHeuaD85InB/IiosZY10tc0PGfuAoUB76HRZrtIizNMrpDtfxO1am/tTcSrvZNgWen1WRmJnEsMiT/HUCduPp4J5JDRrGWKvNRfpOENm99e6vr6mWeTiyMYx0nNZUrq+zwMHRa6yu7BVylCaUgumF60ryQZbvWUKgHkfGCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731575781; c=relaxed/simple; bh=3IlxANAnuFAQJPKpRYOXxLSDlXSqNtW7LiVOTZMygUs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pSkmPzMsVbC/CMCXtzhOh9SKWw+1KuozZPFj0ckFJEKnd2XRAslWONK12AR70LiFKtGbKkWobzzrwkrf8vKDG25UReX4RIvtR7mZGJ4K/bsCcCXbr8Gr7ymQXPLMoBnDjXpZUeF4Pm1gsop+LtrMPF+VDN8gOZInNMkOuoSzqpw= 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=BiH3C02a; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=6rK8swdz; 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="BiH3C02a"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="6rK8swdz" Date: Thu, 14 Nov 2024 10:16:14 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1731575776; 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: in-reply-to:in-reply-to:references:references; bh=3IlxANAnuFAQJPKpRYOXxLSDlXSqNtW7LiVOTZMygUs=; b=BiH3C02aG/1p9MVzbuVoqhLc3bi8qR+/vx/kDr0EtTqDdOFVKZ4/gBfta825yoiWSr6N/k zWFZOKNw4Fhhpew4BeUAYkZ5MeMmv6XNmujoB5ZCbpT1GJlhZe+R27QZR7clCXRibUuRqb ttcKAxZoo2P+n071NeoEX2erkEyJzDCJJUUc7KrrRPUKc69OFKhBxsehyh8XX4czUzlX8q Zq7lU/shg5D6GxU1UtL7Eaz4BN2xQu3hKt13N3eln2Hh2JtfUQ9GMLj2QlYS+LySRjVbNx DtlqUogK13Zjlirmb40JOku0VBw9inmdzE5oaZ57/KRTAXZ0QtT4ei/L6ojFnA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1731575776; 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: in-reply-to:in-reply-to:references:references; bh=3IlxANAnuFAQJPKpRYOXxLSDlXSqNtW7LiVOTZMygUs=; b=6rK8swdz9Q2ueCuq0GmDjxz9ZpnzX/92mbUDuWakuG5bJcudo1m/rquUVPniARh3i/oasQ k4E+6mcryEhb8wAQ== From: Sebastian Andrzej Siewior To: Ankur Arora Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de, paulmck@kernel.org, mingo@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, frederic@kernel.org, efault@gmx.de, sshegde@linux.ibm.com, boris.ostrovsky@oracle.com, Ingo Molnar Subject: Re: [PATCH v2 6/6] sched: warn for high latency with TIF_NEED_RESCHED_LAZY Message-ID: <20241114091614.jSmSI78r@linutronix.de> References: <20241106201758.428310-1-ankur.a.arora@oracle.com> <20241106201758.428310-7-ankur.a.arora@oracle.com> 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 In-Reply-To: <20241106201758.428310-7-ankur.a.arora@oracle.com> On 2024-11-06 12:17:58 [-0800], Ankur Arora wrote: > Add support for warning if the TIF_NEED_RESCHED_LAZY bit is set > without rescheduling for more than the latency_warn_ms period. You fail to explain _why_ it is required to also check TIF_NEED_RESCHED_LAZY to not be set. The problem with NEED_RESCHED set but no scheduling in 100ms is a long preempt-off or IRQ-off region . The problem with NEED_RESCHED_LAZY set but no scheduling in 100ms is a missing timer tick in that time. Also the previous mentioned things might have happen. And the code acting on NEED_RESCHED_LAZY is invoked before this check is. Sebastian