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 84497ECAAA1 for ; Mon, 24 Oct 2022 19:11:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231814AbiJXTLD (ORCPT ); Mon, 24 Oct 2022 15:11:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232262AbiJXTKf (ORCPT ); Mon, 24 Oct 2022 15:10:35 -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 CE88ABB071; Mon, 24 Oct 2022 10:49:39 -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 0F466B81199; Mon, 24 Oct 2022 17:36:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B365EC433B5; Mon, 24 Oct 2022 17:35:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666632958; bh=AK3lqOHcyxajvDoG591jQ3SatKKeHxaZGCF7PwAwWXQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=Cp4O0dtU4VVTruczF4u5BUv+Hk1GV4XQcZ4pxxHmazUwWVZDIZ/+T4jPGBfAAHAsZ pf7DSS6H6I8e8bJdNJPsQibydqltWH4LPuOSCUV4drihCb+fj8RBDNSJKmDqI6dNjV W5qDzdVIULJViqky9gFZ5tYH3L824RNj5jZzZMETymZ7e3n0DQp2qnPdyJPS7Sl8Qv WiBbN2NzpW1W89HOWV2o76KpAw7vGNnzhaJ9+3jZw8Coij4/4ppT8tcSwPQtZHp/vQ RsZtwtJHgHmmMWVcioHH8JP01SBdfY/yNc20JmxdJ12WVTxiC309TKP68pSSmnQDZL nwRc7Ek9EYCHg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 50FA65C0692; Mon, 24 Oct 2022 10:35:58 -0700 (PDT) Date: Mon, 24 Oct 2022 10:35:58 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: Uladzislau Rezki , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org Subject: Re: [PATCH rcu 13/14] workqueue: Make queue_rcu_work() use call_rcu_flush() Message-ID: <20221024173558.GC5600@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20221024031540.GU5600@paulmck-ThinkPad-P17-Gen-1> <20221024153958.GY5600@paulmck-ThinkPad-P17-Gen-1> <20221024164819.GA5600@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 24, 2022 at 01:20:26PM -0400, Joel Fernandes wrote: > On Mon, Oct 24, 2022 at 1:08 PM Uladzislau Rezki wrote: > > > > On Mon, Oct 24, 2022 at 06:55:16PM +0200, Uladzislau Rezki wrote: > > > On Mon, Oct 24, 2022 at 09:48:19AM -0700, Paul E. McKenney wrote: > > > > On Mon, Oct 24, 2022 at 06:25:30PM +0200, Uladzislau Rezki wrote: > > > > > > > > > > > > You guys might need to agree on the definition of "good" here. Or maybe > > > > > > understand the differences in your respective platforms' definitions of > > > > > > "good". ;-) > > > > > > > > > > > Indeed. Bad is when once per-millisecond infinitely :) At least in such use > > > > > workload a can detect a power delta and power gain. Anyway, below is a new > > > > > trace where i do not use "flush" variant for the kvfree_rcu(): > > > > > > > > > > > > > > > 1. Home screen swipe: > > > > > rcuop/0-15 [003] d..1 1792.767750: rcu_batch_start: rcu_preempt CBs=1003 bl=10 > > > > > rcuop/2-33 [002] d..1 1792.771717: rcu_batch_start: rcu_preempt CBs=934 bl=10 > > > > > rcuop/3-40 [001] d..1 1794.811816: rcu_batch_start: rcu_preempt CBs=1508 bl=11 > > > > > rcuop/1-26 [003] d..1 1797.116382: rcu_batch_start: rcu_preempt CBs=2127 bl=16 > > > > > rcuop/4-48 [001] d..1 1797.124422: rcu_batch_start: rcu_preempt CBs=95 bl=10 > > > > > rcuop/5-55 [002] d..1 1797.124731: rcu_batch_start: rcu_preempt CBs=143 bl=10 > > > > > rcuop/6-62 [005] d..1 1798.911719: rcu_batch_start: rcu_preempt CBs=132 bl=10 > > > > > rcuop/2-33 [002] d..1 1803.003966: rcu_batch_start: rcu_preempt CBs=3797 bl=29 > > > > > rcuop/0-15 [003] d..1 1803.004707: rcu_batch_start: rcu_preempt CBs=2969 bl=23 > > > > > > 2. App launches: > > > > > rcuop/4-48 [005] d..1 1831.087612: rcu_batch_start: rcu_preempt CBs=6141 bl=47 > > > > > rcuop/7-69 [007] d..1 1831.095578: rcu_batch_start: rcu_preempt CBs=5464 bl=42 > > > > > rcuop/5-55 [004] d..1 1832.703571: rcu_batch_start: rcu_preempt CBs=8461 bl=66 > > > > > rcuop/0-15 [004] d..1 1833.731603: rcu_batch_start: rcu_preempt CBs=2548 bl=19 > > > > > rcuop/1-26 [006] d..1 1833.743691: rcu_batch_start: rcu_preempt CBs=2567 bl=20 > > > > > rcuop/2-33 [006] d..1 1833.744005: rcu_batch_start: rcu_preempt CBs=2359 bl=18 > > > > > rcuop/3-40 [006] d..1 1833.744286: rcu_batch_start: rcu_preempt CBs=3681 bl=28 > > > > > rcuop/4-48 [002] d..1 1838.079777: rcu_batch_start: rcu_preempt CBs=10444 bl=81 > > > > > rcuop/7-69 [001] d..1 1838.080375: rcu_batch_start: rcu_preempt CBs=12572 bl=98 > > > > > <...>-62 [002] d..1 1838.080646: rcu_batch_start: rcu_preempt CBs=14135 bl=110 > > > > > rcuop/6-62 [000] d..1 1838.087722: rcu_batch_start: rcu_preempt CBs=10839 bl=84 > > > > > <...>-62 [003] d..1 1839.227022: rcu_batch_start: rcu_preempt CBs=1834 bl=14 > > > > > <...>-26 [001] d..1 1839.963315: rcu_batch_start: rcu_preempt CBs=5769 bl=45 > > > > > rcuop/2-33 [001] d..1 1839.966485: rcu_batch_start: rcu_preempt CBs=3789 bl=29 > > > > > <...>-40 [001] d..1 1839.966596: rcu_batch_start: rcu_preempt CBs=6425 bl=50 > > > > > rcuop/2-33 [005] d..1 1840.541272: rcu_batch_start: rcu_preempt CBs=825 bl=10 > > > > > rcuop/2-33 [005] d..1 1840.547724: rcu_batch_start: rcu_preempt CBs=44 bl=10 > > > > > rcuop/2-33 [005] d..1 1841.075759: rcu_batch_start: rcu_preempt CBs=516 bl=10 > > > > > rcuop/0-15 [002] d..1 1841.695716: rcu_batch_start: rcu_preempt CBs=6312 bl=49 > > > > > rcuop/0-15 [003] d..1 1841.709714: rcu_batch_start: rcu_preempt CBs=39 bl=10 > > > > > rcuop/5-55 [004] d..1 1843.112442: rcu_batch_start: rcu_preempt CBs=16007 bl=125 > > > > > rcuop/5-55 [004] d..1 1843.115444: rcu_batch_start: rcu_preempt CBs=7901 bl=61 > > > > > rcuop/6-62 [001] dn.1 1843.123983: rcu_batch_start: rcu_preempt CBs=8427 bl=65 > > > > > rcuop/6-62 [006] d..1 1843.412383: rcu_batch_start: rcu_preempt CBs=981 bl=10 > > > > > rcuop/0-15 [003] d..1 1844.659812: rcu_batch_start: rcu_preempt CBs=1851 bl=14 > > > > > rcuop/0-15 [003] d..1 1844.667790: rcu_batch_start: rcu_preempt CBs=135 bl=10 > > Definitely better, but I'd still ask why not just rely on the lazy > batching that we now have, since it is a memory pressure related > usecase. Or another approach could be, for CONFIG_RCU_LAZY, don't > disturb the lazy-RCU batching by queuing these "free memory" CBs; and > instead keep your improved kvfree_rcu() batching only for > !CONFIG_RCU_LAZY. Given that making the kvfree_rcu()-level batching conditional on CONFIG_RCU_LAZY would complicate the code, what bad thing happens when keeping the kvfree_rcu-level batching unconditionally? Thanx, Paul