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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93493C433FE for ; Mon, 17 Oct 2022 14:07:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230246AbiJQOHe (ORCPT ); Mon, 17 Oct 2022 10:07:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230019AbiJQOHb (ORCPT ); Mon, 17 Oct 2022 10:07:31 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C62B85A8AE; Mon, 17 Oct 2022 07:07:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 8B68CB816C8; Mon, 17 Oct 2022 14:07:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42E53C433D6; Mon, 17 Oct 2022 14:07:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666015647; bh=Tfyuyfd8ko9kq+ZnL6uDRnJeD6vmcal8pGXr1suuHzw=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=ZfIfuHIcChse80XDt+7NMqXzrdmxJmNIfBePT8dR886wglj7x6rSOboVLKPBbqMdH 9uMpIGHyr/cE0nzU2bBWc2X4isdlLkzRXoL9ZoFPgZgig14SFnOb2vMkAy6M6soZXm VWx6gQHG2y5sNFEpTFs2Mg2z4yGZTcg1TscWFkI7vFwVSLuykS80v3TVvF5TJ99mB3 /1S7CmCzFDn7QCtrKX2hMFrbyncRzfjl29Uzh4kxLe6uIZLs0jqZCJFYEPJCNNgDPq KCvyCBjS7gxnPywVpv4Oqk6VpbEajRiye7+/bRm5vbK/yqYs4ogkz061uyT7os54Hf kZCGuV6Tqvblg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id D4B1D5C0622; Mon, 17 Oct 2022 07:07:26 -0700 (PDT) Date: Mon, 17 Oct 2022 07:07:26 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, frederic@kernel.org Subject: Re: [PATCH v9 00/13] rcu: call_rcu() power improvements Message-ID: <20221017140726.GG5600@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20221016162305.2489629-1-joel@joelfernandes.org> <20221017133738.GE5600@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 17, 2022 at 09:47:00AM -0400, Joel Fernandes wrote: > On Mon, Oct 17, 2022 at 9:37 AM Paul E. McKenney wrote: > > > > On Sun, Oct 16, 2022 at 04:22:52PM +0000, Joel Fernandes (Google) wrote: > > > v9 version of RCU lazy patches based on rcu/next branch. > > > Only change since v8 is this discussion: > > > https://lore.kernel.org/rcu/20221011180142.2742289-1-joel@joelfernandes.org/T/#m8eff15110477f3430b3b02561b66f7b0d34a73b0 > > > > > > To facilitate easier merge, I dropped tracing and other patches and just > > > implemented the new changes. I will post the tracing patches later along with > > > rcutop as I need to add new tracepoints that Frederic suggested. > > > > > > Main recent changes: > > > 1. rcu_barrier() wake up only for lazy bypass list. > > > 2. Make all call_rcu() default-lazy and add call_rcu_flush() API. > > > 3. Take care of some callers using call_rcu_flush() API. > > > 4. Several refactorings suggested by Paul/Frederic. > > > 5. New call_rcu() to call_rcu_flush() conversions by Joel/Vlad/Paul. > > > > > > I am seeing good performance and power with these patches on real ChromeOS x86 > > > asymmetric hardware. > > > > > > Earlier cover letter with lots of details is here: > > > https://lore.kernel.org/all/20220901221720.1105021-1-joel@joelfernandes.org/ > > > > [...] > > > > Very good, thank you all! > > > > I have pulled these in for further review and testing. > > > > I am holding off on the last one ("rcu/debug: Add wake-up debugging for > > lazy callbacks") for the immediate future, but let's see how it goes. > > Thanks! And nice timing with RCU just turning 20 years old ;-) Yes, 20 years old, but with the qualifier "in the Linux kernel". ;-) RCU was in DYNIX/ptx for almost ten years prior to that. And mechanisms vaguely resembling RCU go back to Kung's and Lehman's 1980 paper entitled "Concurrent Manipulation of Binary Search Trees". And maybe farther, but that is the oldest citation I know of. Thanx, Paul > - Joel > > > > > > > > Thanx, Paul > > > > > Frederic Weisbecker (1): > > > rcu: Fix missing nocb gp wake on rcu_barrier() > > > > > > Joel Fernandes (Google) (9): > > > rcu: Make call_rcu() lazy to save power > > > rcu: Refactor code a bit in rcu_nocb_do_flush_bypass() > > > rcuscale: Add laziness and kfree tests > > > percpu-refcount: Use call_rcu_flush() for atomic switch > > > rcu/sync: Use call_rcu_flush() instead of call_rcu > > > rcu/rcuscale: Use call_rcu_flush() for async reader test > > > rcu/rcutorture: Use call_rcu_flush() where needed > > > rxrpc: Use call_rcu_flush() instead of call_rcu() > > > rcu/debug: Add wake-up debugging for lazy callbacks > > > > > > Uladzislau Rezki (2): > > > scsi/scsi_error: Use call_rcu_flush() instead of call_rcu() > > > workqueue: Make queue_rcu_work() use call_rcu_flush() > > > > > > Vineeth Pillai (1): > > > rcu: shrinker for lazy rcu > > > > > > drivers/scsi/scsi_error.c | 2 +- > > > include/linux/rcupdate.h | 7 ++ > > > kernel/rcu/Kconfig | 15 +++ > > > kernel/rcu/lazy-debug.h | 154 +++++++++++++++++++++++++++ > > > kernel/rcu/rcu.h | 8 ++ > > > kernel/rcu/rcuscale.c | 70 +++++++++++- > > > kernel/rcu/rcutorture.c | 16 +-- > > > kernel/rcu/sync.c | 2 +- > > > kernel/rcu/tiny.c | 2 +- > > > kernel/rcu/tree.c | 149 ++++++++++++++++++-------- > > > kernel/rcu/tree.h | 12 ++- > > > kernel/rcu/tree_exp.h | 2 +- > > > kernel/rcu/tree_nocb.h | 217 ++++++++++++++++++++++++++++++++------ > > > kernel/workqueue.c | 2 +- > > > lib/percpu-refcount.c | 3 +- > > > net/rxrpc/conn_object.c | 2 +- > > > 16 files changed, 565 insertions(+), 98 deletions(-) > > > create mode 100644 kernel/rcu/lazy-debug.h > > > > > > -- > > > 2.38.0.413.g74048e4d9e-goog > > >