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=-3.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_AGENT_GIT autolearn=ham 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 23C4BC10F03 for ; Tue, 23 Apr 2019 18:45:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC06821738 for ; Tue, 23 Apr 2019 18:45:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=digitalocean.com header.i=@digitalocean.com header.b="CVrjjQ79" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726448AbfDWSpo (ORCPT ); Tue, 23 Apr 2019 14:45:44 -0400 Received: from mail-io1-f67.google.com ([209.85.166.67]:35499 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbfDWSpn (ORCPT ); Tue, 23 Apr 2019 14:45:43 -0400 Received: by mail-io1-f67.google.com with SMTP id r18so12659446ioh.2 for ; Tue, 23 Apr 2019 11:45:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digitalocean.com; s=google; h=from:to:cc:subject:date:message-id:in-reply-to; bh=PpIY/pcnE8PBkyei4ABYv/OQrwv3IcaKyfbDF2jVX5Y=; b=CVrjjQ79twfN3qUGnu9RF9vLUZRZgnnyGEY9+HC4F/AFQ6h7/TWGxXKvY9e2McBiv1 1tpqkCl5PTZtO/dqZSEfXrqjW6xrVYCOr8kXHv3uYKS4JzKGlFdDnr6sGpeGCxF0WBoN R4FcruV/ul0RmcXQvWtueX6jaZibLjqR1uM4w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to; bh=PpIY/pcnE8PBkyei4ABYv/OQrwv3IcaKyfbDF2jVX5Y=; b=EYSx6fIN+SELXS+81Rd9DlhvEKlLuEqQAOxvmk89HaFAx16SI73ziUOe1ctHKTNZtN cj5JDmbizBpoDkl/4auO78eT8Fpd8jGl1GwA4f0LHKntXAEuiNCCmZMPKxTkk6K2wwtP 450HpFUh86gvDXV6dS1GIIYUV7Z7DXTfuDI3DDiAVc22oDyRJCPcYQwGYupKec44+FFo 7Ii7ePNYosQNo2E6bINmrLY9ZmkGm48B2PiEQFyb5+G6esfOuKLWhTYFs7xMJ7sPFb0l EvvZsMZUBlhgjK0cTxpGHqOVTrxN+aP/Tu1Ty5toQxBdvAC8JWhfyHyN1iEQVs5N5Alx +giA== X-Gm-Message-State: APjAAAWa7kkwfs/+4z69VSHlroONU1j8hszpHK9q2DGYjspfHLaDyKZV p8hX60ji3fE/E+kDd8s6yYIpaA== X-Google-Smtp-Source: APXvYqxiNo3NI2pEyiLFV4zIgDZnYuZDR3NysCSKEZjvMGjMjqkJEFoI5uh5jSmSwW22RGDJ6Av7fg== X-Received: by 2002:a6b:6909:: with SMTP id e9mr11910764ioc.208.1556045142479; Tue, 23 Apr 2019 11:45:42 -0700 (PDT) Received: from swap-tester ([178.128.225.14]) by smtp.gmail.com with ESMTPSA id n199sm8075806itn.34.2019.04.23.11.45.41 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 23 Apr 2019 11:45:41 -0700 (PDT) From: Vineeth Remanan Pillai To: Phil Auld Cc: Vineeth Remanan Pillai , Nishanth Aravamudan , Julien Desfossez , Peter Zijlstra , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Aaron Lu , Aubrey Li , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini Subject: Re: [RFC PATCH v2 00/17] Core scheduling v2 Date: Tue, 23 Apr 2019 18:45:27 +0000 Message-Id: <20190423184527.6230-1-vpillai@digitalocean.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190423180238.GG22260@pauld.bos.csb> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> - Processes with different tags can still share the core > I may have missed something... Could you explain this statement? > This, to me, is the whole point of the patch series. If it's not > doing this then ... what? What I meant was, the patch needs some more work to be accurate. There are some race conditions where the core violation can still happen. In our testing, we saw around 1 to 5% of the time being shared with incompatible processes. One example of this happening is as follows(let cpu 0 and 1 be siblings): - cpu 0 selects a process with a cookie - cpu 1 selects a higher priority process without cookie - Selection process restarts for cpu 0 and it might select a process with cookie but with lesser priority. - Since it is lesser priority, the logic in pick_next_task doesn't compare again for the cookie(trusts pick_task) and proceeds. This is one of the scenarios that we saw from traces, but there might be other race conditions as well. Fix seems a little involved and We are working on that. Thanks