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 11D4FC433FE for ; Tue, 22 Nov 2022 20:17:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234780AbiKVURv (ORCPT ); Tue, 22 Nov 2022 15:17:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234775AbiKVURp (ORCPT ); Tue, 22 Nov 2022 15:17:45 -0500 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B4152DDE for ; Tue, 22 Nov 2022 12:17:41 -0800 (PST) Received: by mail-pl1-x629.google.com with SMTP id y4so14746604plb.2 for ; Tue, 22 Nov 2022 12:17:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=fOGHLP5HIj9i23WKx8F5fFOZNnqfBffKUE8KWY64clY=; b=NzS91rjsOTy4kDCWDLyGmvr/liq0C+vIn2YjV7FPq/+cVzAyEUBzFgeBbzmM0vCVV/ Y+iw3mdzeZeuWffmnbFvxcH2BksFpC6t5Fyggd/KXkRP/EITa9rqx6cMOQ9+wGoz91/j OVqTCPzqQZSDVS16WuvYwfmJ7QgcEpvttLaBcXeCJgaLi9qDwnl1qgpjK2gp0+3kvQQG /mIrAG/w1qw1D7RFPu2V0lET6GHsd8sD3mcatlRrY/L3YkkDCu+/KEtC/arvJ5/+0HSr Y8L1g6NUlRa7OMA9O6QfvUcUd3k1j1T0kVhad4BkwxWF43mdVjBtDCyvOQDMcWX3U9kc 9x7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=fOGHLP5HIj9i23WKx8F5fFOZNnqfBffKUE8KWY64clY=; b=HEMga9gluY+EtzJklxInhSQwgrEQY2Df5G2a4rhDxMTTTsws4Upjlu8eSQtjoIMCag hOw9zV0+RvX1qlV0MY2onaKg1A8P/svtBhtO//VRIbgRosiu3g4BzMhmvs4NcIIkobhA azk0wMBCjerz8KoeCeLEbnSxRpgkb6jS3frUnri+gQj8pHjTRyDgGqYGZIJOdrDwxazu b1j0SMePU75uvZJ/ANxHg1WCRmcVFMlzUPLiRBd4J/ObdOQ1vE3qfP8ND9pMHwZ50wVJ 9XyCf1VTtKWexuWBUjWTETJqf8yeruzoGCqBdTzpJ4y7lTk+IWYYeOusgNZkPvuN5r+5 wG2g== X-Gm-Message-State: ANoB5pnVt0+L4prBPQHCTG+C89AVHTzdwsM/gKEYvqy8pG9/ZMqiFniK wfPCRzM029HCIPJwHhRU3vc= X-Google-Smtp-Source: AA0mqf5/yZRUWfzUlv412lMPgmSdCkAtoLh+djHTvtSi4lmtwQ3l5XgkObKKpA/+gUDC4sw7olEwdQ== X-Received: by 2002:a17:902:cccd:b0:186:fd58:c706 with SMTP id z13-20020a170902cccd00b00186fd58c706mr5786135ple.4.1669148261037; Tue, 22 Nov 2022 12:17:41 -0800 (PST) Received: from localhost ([2620:10d:c090:400::5:bb3]) by smtp.gmail.com with ESMTPSA id y15-20020a17090264cf00b00188f9534a3esm11050639pli.87.2022.11.22.12.17.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Nov 2022 12:17:40 -0800 (PST) Sender: Tejun Heo Date: Tue, 22 Nov 2022 10:17:39 -1000 From: Tejun Heo To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, Lai Jiangshan , Peter Zijlstra , Frederic Weisbecker , Juri Lelli , Phil Auld , Marcelo Tosatti Subject: Re: [PATCH v5 3/5] workqueue: Make too_many_workers() return the worker excess Message-ID: References: <20221122192937.2386494-1-vschneid@redhat.com> <20221122192937.2386494-4-vschneid@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221122192937.2386494-4-vschneid@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Tue, Nov 22, 2022 at 07:29:35PM +0000, Valentin Schneider wrote: ... > The function currently returns true when > (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy > thus, the desired number of idle workers is expressed by > (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO == nr_busy - 1 > IOW > nr_idle == ((nr_busy - 1) / MAX_IDLE_WORKERS_RATIO) + 2 > +/* How many idle workers should we get rid of, if any? */ > +static unsigned int worker_cull_count(struct worker_pool *pool) Can we name it nr_workers_to_cull()? > { > bool managing = pool->flags & POOL_MANAGER_ACTIVE; > int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ > int nr_busy = pool->nr_workers - nr_idle; > > - return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; > + lockdep_assert_held(&pool->lock); > + > + /* > + * We keep at least 2 spare idle workers, but overall aim to keep at > + * most (1 / MAX_IDLE_WORKERS_RATIO) workers idle. > + */ > + return max(0, nr_idle - 2 - ((nr_busy - 1) / MAX_IDLE_WORKERS_RATIO)); I think we can do away with the subtraction on nr_busy. I don't think it'd make any material difference, so maybe we can do: return max(0, nr_idle - 2 - nr_busy / MAX_IDLE_WORKERS_RATIO); Thanks. -- tejun