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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 1DE0BC0650E for ; Mon, 1 Jul 2019 13:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E38E221721 for ; Mon, 1 Jul 2019 13:53:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="XWregEDl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727959AbfGANxt (ORCPT ); Mon, 1 Jul 2019 09:53:49 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:42874 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727752AbfGANxt (ORCPT ); Mon, 1 Jul 2019 09:53:49 -0400 Received: by mail-pg1-f193.google.com with SMTP id t132so2731526pgb.9 for ; Mon, 01 Jul 2019 06:53:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=CnqcdAZEqlhe5AvSTX+V5wDK1OqDo6RCXWT/qry/0jg=; b=XWregEDl1FFMPhgi4vXgSGCiek/WrfkHRgLPn5FgA3IxY5gqLSnf+5oM7t9Shhq0tn k9ig4d4b372SkcPvNZ2VUnZfZjIBURPZFmBU8+pS1u5GZpAe/nX6VsDTDksvNUpBbxkc ttX2Jr0lLx1e8hSiszEog64NrgL4txrFPVS4k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=CnqcdAZEqlhe5AvSTX+V5wDK1OqDo6RCXWT/qry/0jg=; b=YXbhi1JPJEab/gK7Rlb+cUiUhFEiDTc2czdaEwv8eR7uB0ScwKdUiuDosXelgiPOoi aZTG9qju32EkQ9OGqDEr40QVnJeSbgT+lWtw7SBUj6+S6kR+BF0i/CETcPayHdvFjo2X TeIHqI1+r/YL4sfwIliNhUsPo4UqQTiEiO0yRZXfN6O5WnLImbHC3y9YAGcBS7tjdQlQ 3TawyieHU4BwvmtCuRlIgiJoW0TO1ErrUlgrpmB6mL0SU37zGZOvKZ5m28wEVPfqJwQV OL9GeYa0TyA1ozGV6nCE/RvcLXoD1goEGdC8/ROn/RBm52FGi/ZGfuJC+dOdIOYKAdRV x8Iw== X-Gm-Message-State: APjAAAXqoRD5wbd8noQwwnkpY/E9/D50J3VNd/as50yXYDx+lC3d0WM1 P1r5WIX/qUkjXRXY5GWKnm3I3A== X-Google-Smtp-Source: APXvYqxX5xXZI0X2mxnuICMgqyXLY+28omTo2AX9jZBNCHB9Nez+eCLHSmiTzqOVBM+4vcQjsnymdA== X-Received: by 2002:a63:7e1d:: with SMTP id z29mr11833928pgc.346.1561989228598; Mon, 01 Jul 2019 06:53:48 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id z13sm11274343pjn.32.2019.07.01.06.53.47 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 01 Jul 2019 06:53:47 -0700 (PDT) Date: Mon, 1 Jul 2019 09:53:46 -0400 From: Joel Fernandes To: linux-kernel@vger.kernel.org Cc: Josh Triplett , kernel-team@android.com, Lai Jiangshan , linux-kselftest@vger.kernel.org, Mathieu Desnoyers , "Paul E. McKenney" , rcu@vger.kernel.org, Sebastian Andrzej Siewior , Shuah Khan , Steven Rostedt Subject: Re: [RFC 1/3] rcu: Expedite the rcu quiescent state reporting if help needed Message-ID: <20190701135346.GA167294@google.com> References: <20190701040415.219001-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190701040415.219001-1-joel@joelfernandes.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, Jul 01, 2019 at 12:04:13AM -0400, Joel Fernandes (Google) wrote: > The t->rcu_read_unlock_special union's need_qs bit can be set by the > scheduler tick (in rcu_flavor_sched_clock_irq) to indicate that help is > needed from the rcu_read_unlock path. When this help arrives however, we > can do better to speed up the quiescent state reporting which if > rcu_read_unlock_special::need_qs is set might be quite urgent. Make use > of this information in deciding when to do heavy-weight softirq raising > where possible. Just fyi, TREE01-06, SRCU-N and SRCU-t passed overnight testing with this series.