From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C4E8C2BA19 for ; Tue, 14 Apr 2020 14:22:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 55547206D5 for ; Tue, 14 Apr 2020 14:22:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ndtMzIgw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389945AbgDNOWb (ORCPT ); Tue, 14 Apr 2020 10:22:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389893AbgDNOW0 (ORCPT ); Tue, 14 Apr 2020 10:22:26 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0779C061A0C for ; Tue, 14 Apr 2020 07:22:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; 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=tla671Fmro8CIHThx1Xf7leHF3ClxMWQwFBU8nfoPaE=; b=ndtMzIgwj7ZmUHHcYr3pyLR8ca jcwbT+zKddchRHAGhucg7kexaPD1tGAYmuJJls4zHeW6GwOj1zIFjSMu++Myrydm64IgXjKWqsub/ fa97XEJpdEjDgcROM2M7O8XpMsd+qe5sdMtTbUd6kP64hYKgfRH15ddB8ACZiF/Sa0uXPrdTxX9dl BTBSpj8q6AoEnt5shPPASCMWodPj2KmFI5KncWzPJ1JS6kt4G6g7Fga0UpbXx1HtvyTUA7iyuc6Fc QdcNkyVJ1R73Y6Lq3pMOlae+ldVsoTLjQwLDExGpsb6wIYeBl0QcC3GrIBhp8JPIsEE/kcIVrm+As pstx3s1g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOMRm-0001u5-VR; Tue, 14 Apr 2020 14:21:55 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 007F63012D8; Tue, 14 Apr 2020 16:21:53 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DCB5F2B22FBE0; Tue, 14 Apr 2020 16:21:52 +0200 (CEST) Date: Tue, 14 Apr 2020 16:21:52 +0200 From: Peter Zijlstra To: vpillai Cc: Nishanth Aravamudan , Julien Desfossez , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Phil Auld , Aaron Lu , Aubrey Li , aubrey.li@linux.intel.com, Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini , Joel Fernandes , joel@joelfernandes.org Subject: Re: [RFC PATCH 00/13] Core scheduling v5 Message-ID: <20200414142152.GV20730@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 04, 2020 at 04:59:50PM +0000, vpillai wrote: > TODO > ---- > - Work on merging patches that are ready to be merged > - Decide on the API for exposing the feature to userland > - Experiment with adding synchronization points in VMEXIT to mitigate > the VM-to-host-kernel leaking VMEXIT is too late, you need to hook irq_enter(), which is what makes the whole thing so horrible. > - Investigate the source of the overhead even when no tasks are tagged: > https://lkml.org/lkml/2019/10/29/242 - explain why we're all still doing this .... Seriously, what actual problems does it solve? The patch-set still isn't L1TF complete and afaict it does exactly nothing for MDS. Like I've written many times now, back when the world was simpler and all we had to worry about was L1TF, core-scheduling made some sense, but how does it make sense today? It's cute that this series sucks less than it did before, but what are we trading that performance for?