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 6E117C67871 for ; Mon, 24 Oct 2022 22:10:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231918AbiJXWJx (ORCPT ); Mon, 24 Oct 2022 18:09:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232642AbiJXWJJ (ORCPT ); Mon, 24 Oct 2022 18:09:09 -0400 Received: from mail-ej1-f45.google.com (mail-ej1-f45.google.com [209.85.218.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74613300719 for ; Mon, 24 Oct 2022 13:23:12 -0700 (PDT) Received: by mail-ej1-f45.google.com with SMTP id sc25so7568066ejc.12 for ; Mon, 24 Oct 2022 13:23:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=Txc2f0xrYtuNhq1WDp0NUqR3NHmxCjbN9kZ+l+jYFng=; b=r4IUWf7GfKNtreUKZa+k5Hp/OOGwlpVrK7mY6ybjeqQkuneWSVPb2m+t6F7b6wGNL9 HvSybdTceQWoZf4QQmL91qUBVjiwpE+0++Dtd9BRlPvUGIAC59uNgqzftOuCJJYQbowa TSGt7TXvw7PDPtIN+djXtGF9iOzu8tx2gPoHw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Txc2f0xrYtuNhq1WDp0NUqR3NHmxCjbN9kZ+l+jYFng=; b=DKDUqDuPfvXsage0c4YPQ+3wvJOVsCsNfv2E8McYQAWhbq1CKnV2H50KTeYwrlKD6a oUx77TFrGB81mQ+zLJqol1imU+hXRoU+3BxMixSmzD/JgUSC673jJyKkyU94vWrWKNPO LZN528fXunOf0rs6R8/mDZ9Ep6uU8UD9Lf+vqpUkAoIuPN8KheI/cK+GepnLb1TBBNqL ZRAVt0SRSS0KIT5mSY1YyTDk8+cfBq7++OQ2CqnvAz/wEW1jwxqlBNJ4YwDOP794qe3J w2HsWusJmadHYJ+ucnAKl0o6SOfTQfggSx9ivUtZHcc0C3c/e2jwz2EgBzdBmN0yJ8oV t34A== X-Gm-Message-State: ACrzQf01XaoK0OWvZpjBCI3/LZQ6wG09QYS12emRWm70fHjnKIZA1EJi fh7YPI4GTlq4IGKwCVjq5G9wnbeQcLdUbb/JRYfnOg== X-Google-Smtp-Source: AMsMyM4wB5UlgJkJ01+AQ/adqbN/c5JCCGzNmpiQDtjELOavXx8rHS8kGK4ZZC4BFyyXgnGIQoSFHRcNXcra0y8cUbM= X-Received: by 2002:a17:907:2cf1:b0:78d:c7a1:172d with SMTP id hz17-20020a1709072cf100b0078dc7a1172dmr28624971ejc.51.1666642591752; Mon, 24 Oct 2022 13:16:31 -0700 (PDT) MIME-Version: 1.0 References: <20221024031540.GU5600@paulmck-ThinkPad-P17-Gen-1> <20221024153958.GY5600@paulmck-ThinkPad-P17-Gen-1> <20221024164819.GA5600@paulmck-ThinkPad-P17-Gen-1> <20221024173558.GC5600@paulmck-ThinkPad-P17-Gen-1> In-Reply-To: From: Joel Fernandes Date: Mon, 24 Oct 2022 16:16:20 -0400 Message-ID: Subject: Re: [PATCH rcu 13/14] workqueue: Make queue_rcu_work() use call_rcu_flush() To: paulmck@kernel.org Cc: Uladzislau Rezki , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 24, 2022 at 4:12 PM Joel Fernandes wrote: > > On Mon, Oct 24, 2022 at 1:36 PM Paul E. McKenney wrote: > > > > 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? > > The bad thing happening is power impact. There is a noticeable impact > in our testing, and when we dropped this particular patch, it got much > better results. > > I also run rcutop and I see without the patch that I have several > seconds of laziness at a time, unlike with the patch. > > Even in the beginning when I came up with an implementation for > call_rcu_lazy(), I had to mark queue_rcu_work() as lazy as well since > it was quite frequent (on ChromeOS). But when we introduced the > flush() API, I forgot to not use flush() on it. But unfortunately > this patch slipped into my last series when Vlad and I were debugging > the SCSI issue, and did not really help for the SCSI issue itself. I could try to run Vlad's other mainline patch itself and measure power, I'll get back on that. Thanks!