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 A9F181F949 for ; Mon, 2 Dec 2024 09:58:55 +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=1733133537; cv=none; b=qAsI/D+3thOQKd8fMBHbBL4wg448O5ECGnWrOmRWGT7InhwDLImETCEhOr29NfySilvtX0f/STL37OvpS8/38HbDCUMtw6Fgr/FMJnVwDGbxOioixVqbpwCDToTSjA8bkk9BZowvDd9aI56Kd1j1gOq9PWd7pstevch7Fg4lRKU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733133537; c=relaxed/simple; bh=4l2BJnDnqRwMBQWsb/m/LfpV9YNxXPR5iKJQ8ycwhsU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=vGFvf/dKMbOmAtNkqa5BVpviDsIdHTofwyviqMEDR8wDzalaka3hY9R7q1Al5Nxof4D+SvkCW9yJYxd+VXmsfddHi70UylUpv1+ia1Dfq4ZGTJP6AMPCSbHPfHoF5h7RwqImNqlZnIzP7q8+as1umpBf8/XU4G0/u516zfb1xq4= 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=LnTKyjxd; 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="LnTKyjxd" 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=/pmSJ6r9IAvyarU/N87P9IsIoLsbj7PYkhCwKxu9feY=; b=LnTKyjxd2IG/myALp33e0JQoZo D6b3NgB+OsjC05JZfvTuuQ+M9hYnj9uVLLvh0v+xMeu7Du2EBlzfzdd0QsZG26cA3Vc9lBbWdtY2m RlAbkGIYnKHlKwMf+k0uAq+HJxJtcsrav7/CmW8k9ZiPyPn/p9pU51y6TEKQmxZWmEtv7s5mVDCRK QWu8Tlfk3lhJeyuSJFo8WL+tvcxGKkA38YESzEpLqSOSWuamAvDRKptqmzHvB8Cr1V0qyWt/G1zAR K0TGuSC+MJw5zlqtdyN/XwbV5T/an6TBcUHzTq0QXQDtvGu+ebiOvx7NLByXGe9bEpNLvRaTVcCK4 tJsle9UQ==; Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tI3Ca-000000029Nr-3San; Mon, 02 Dec 2024 09:58:49 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 002B1300402; Mon, 2 Dec 2024 10:58:47 +0100 (CET) Date: Mon, 2 Dec 2024 10:58:47 +0100 From: Peter Zijlstra To: Changwoo Min Cc: tj@kernel.org, void@manifault.com, mingo@redhat.com, changwoo@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/5] sched_ext: Manage the validity of scx_rq_clock Message-ID: <20241202095847.GK24400@noisy.programming.kicks-ass.net> References: <20241202043849.1465664-1-changwoo@igalia.com> <20241202043849.1465664-3-changwoo@igalia.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=us-ascii Content-Disposition: inline In-Reply-To: <20241202043849.1465664-3-changwoo@igalia.com> On Mon, Dec 02, 2024 at 01:38:46PM +0900, Changwoo Min wrote: > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 95e40895a519..ab8015c8cab4 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -789,6 +789,7 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) > void update_rq_clock(struct rq *rq) > { > s64 delta; > + u64 clock; > > lockdep_assert_rq_held(rq); > > @@ -800,11 +801,14 @@ void update_rq_clock(struct rq *rq) > SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED); > rq->clock_update_flags |= RQCF_UPDATED; > #endif > + clock = sched_clock_cpu(cpu_of(rq)); > + scx_rq_clock_update(rq, clock); This adds a write to a second cacheline for *everyone* always. Please don't do that.