From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 965C418E3F for ; Fri, 2 May 2025 14:35:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746196554; cv=none; b=V6+l0SnXNiexqPbAfgnVlN36C2Sj9nsTXKSWCX+Gt6lNufNC3LpuiL01/6BvDbvRU23/mLBDqTNXrPvCRqMEdK2SG6VGgSD+uSDXLFBukFCPmuRiBX5sPSl8BZjDW70G83eigx0P1nWckKlQ8CgWvp0AQ5jljheRIG3b4DGbUiA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746196554; c=relaxed/simple; bh=ARWyjDur8yjCBSeTQOV6z1pA+12Zrb+wPZ5kWTaPM7g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I553hM6R6i28E9lOZra7KvhV+rEUzChAU7TU/6r1y9IL/xRUuTCjTVN5tnbRGPiXHFC7fyZUVZLiQ5+pDz+ob/7dVEhkOP5xeNvad1N+8jFN1yVr+Golbb5TaIV3XECJli7C3eoKEPyDX7JxV3TXRecUvyYUkY+qK9dUYVi3MMs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=C6JciLWf; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="C6JciLWf" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=UbAG8iInp9ePuVcNeFLqHQPxcdJSZ1IQ2sJpc0Vp0h0=; b=C6JciLWf3x/ELUskxzsb2MTsmL Ksb2suhhaF2ZSeKe+l8q6pBYe0Yc9gMqqIOMZ/WasmfviyzTvwAxW+xIrL0HtLkKQUmcrEBYgfnEb V7WNHjiA1IumPvvE9RWjSqQ2Vl81aj99VmEGUGPAPhr88ZUrvs3/ve2ADuFV9eonLTcnGVC3qCsrq yms1Bm/y1+Wm1N/zpXGOzbM2Mi6f52+ahnkdqKzwjtH/TjuRNBOff/GC/oSkeiY2ojtjEDy5sf5rY 5ONAZ7nuWryi5BA5BZLB6hhMBP+B1OuLaR2NCOGrM1BtBeuA0zXshlwHg2UQHV0pYXpkO8kVaUfzo xROEjAEQ==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.1 #2 (Red Hat Linux)) id 1uArUP-0000000Ezmp-09yi; Fri, 02 May 2025 14:35:45 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 97AE230057C; Fri, 2 May 2025 16:35:44 +0200 (CEST) Date: Fri, 2 May 2025 16:35:44 +0200 From: Peter Zijlstra To: Sebastian Andrzej Siewior Cc: Prakash Sangappa , linux-kernel@vger.kernel.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, kprateek.nayak@amd.com Subject: Re: [PATCH V3 1/4] Sched: Scheduler time slice extension Message-ID: <20250502143544.GW4439@noisy.programming.kicks-ass.net> References: <20250502015955.3146733-1-prakash.sangappa@oracle.com> <20250502015955.3146733-2-prakash.sangappa@oracle.com> <20250502123433.AHDVLZdY@linutronix.de> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250502123433.AHDVLZdY@linutronix.de> On Fri, May 02, 2025 at 02:34:33PM +0200, Sebastian Andrzej Siewior wrote: > On 2025-05-02 01:59:52 [+0000], Prakash Sangappa wrote: > > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > > index 20154572ede9..b26adccb32df 100644 > > --- a/kernel/entry/common.c > > +++ b/kernel/entry/common.c > > @@ -98,8 +99,12 @@ __always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs, > > > > local_irq_enable_exit_to_user(ti_work); > > > > - if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) > > - schedule(); > > + if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) { > > I asked to limit this to LAZY only. No -- this should work irrespective of the preemption model chosen. It should also have a default time that is shorter than the scheduling delay normally observed. It should probably also have a PR_WARN on raising the sysctl value. I know you worry about RT, but show me a trace where it is a problem.