Received: by 2002:a05:6a10:8c0a:0:0:0:0 with SMTP id go10csp3972619pxb; Mon, 8 Feb 2021 05:04:33 -0800 (PST) X-Google-Smtp-Source: ABdhPJzDUxFjCeEX7OnWG6tN354jmqpblMxpu7Gugo+EMPo1nLmgXl1CcbjFFFgPwBeJnm3Q8mF8 X-Received: by 2002:a05:6402:151:: with SMTP id s17mr16408792edu.107.1612789473177; Mon, 08 Feb 2021 05:04:33 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1612789473; cv=none; d=google.com; s=arc-20160816; b=RH+YLYvR7g9+Amk3Mu8Z1UgeY/QI+SHmH/Tv7XF6QyLoZBRZ8fjDc5AT3bpKMUcOm6 iFvkEDtDCCvd6pp2cVeEQJz+VPDmimkyRw85MtNF852JxZ8jgkVsp9DKyM/ioKIKYbEe vtyWgiSfzB4TAY0rtJ7o/JL5CmoXFlzWtbNsbr7XFaIbff+2ZykzszesFF14yK/ew/13 olrYmbA4p54h2svAT2rVhI6sHXiyGF94J0fNrh4Imstr1kYUej3zbARDUdMKSNu0uX/Q GOfTx8RGO8C14ZD5vbtp8k0xFaJIjnuGF+RIxYubK2t2sA5Z9D66lz/lAfTHJjbuTkkE lWtw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:user-agent:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:date:from :dkim-signature; bh=b7Ntd6xk8fkmmQrfnT7+pjI8yRVrY36ISzhp9gp/+qo=; b=SBiDZWgDZpiqiN91tCuQNNlvwhWZ1a+lJ4KTB4AabyLd30r5QvUbidwUmlagSsZvgi zgIZU2z/bsgccHoHQ6iD30sesDSsXMPvwIqSPvV6CZm2xXs33oy0orolccmgEAC+qISu FqssffOoO4FCS6BjaR4h8G5aM22UJRu33Y8iXL82y5HtoTuleRpkL6qAMcJ3iycOO8xK rbnRqv8Zd0DlB8YcO+LOXkZjDTqZoknZEAhdT7NcADDfzsdbg4xDRE922wBUZu+OcgGk nGNb48lJ6ABU9ysCVTdIF44HPseu+aSqubwGgHpVUwOH72E8hdgYemTY4MmcgtToxH/T Cdtw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=UVeArX5d; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id j4si11251777ejv.17.2021.02.08.05.04.08; Mon, 08 Feb 2021 05:04:33 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=UVeArX5d; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229756AbhBHNDe (ORCPT + 99 others); Mon, 8 Feb 2021 08:03:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229623AbhBHNDc (ORCPT ); Mon, 8 Feb 2021 08:03:32 -0500 Received: from mail-lj1-x22d.google.com (mail-lj1-x22d.google.com [IPv6:2a00:1450:4864:20::22d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3774C061756; Mon, 8 Feb 2021 05:02:51 -0800 (PST) Received: by mail-lj1-x22d.google.com with SMTP id e18so16811731lja.12; Mon, 08 Feb 2021 05:02:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=b7Ntd6xk8fkmmQrfnT7+pjI8yRVrY36ISzhp9gp/+qo=; b=UVeArX5dnnbdSZZLXOLVozsw5KFWX5lk9rUACersqUl4CpkRCuGnY0ory/J1XjXE9p M8cls28C8CxvqL0kNW0TuUOKjSESUmswORaVL0A/P/YUnuphVychrZFw7iyiNv2F7/1W AT0zQZ4hgtfXbB6OvdHnSbZKPwRznrt9GXKNjRwWriPmrPm/EmUhX2bdl2pFEj+3V3nY cz07yjwEjhAkatoVve5Rhgqn18EYtR2vV1hWrAgsis59QemJfV/9+VERlc5WDQ9n/14z p7tFTm18GDI8DYExi4z/wnraZgHdm7cpsObgaNG5JuWnxJqKI6d2PdqqkzDHoHZkwoAg eMkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=b7Ntd6xk8fkmmQrfnT7+pjI8yRVrY36ISzhp9gp/+qo=; b=UuX/VatsuGUo7KCO3aQHH9MhtFIGcG7CBUKHxnmm/lCnQpNJpn79SNK+hEIAcC41Bs phZ0xvjO3C4BXiT0zaFzlEfjLBRoT0aOTtOljJma4kMmR/n3efpW2sOaw5zFQqashH60 ZJgXBrR/iDAJpFY+187Od48TB9bHkiViA5oTo5iBlSc5SRNun4FDTEQ5ScFv0UVIDv9u DDFy2AdVVaDqb2UYYcrBW2gEUUJHhwb6bQlDZInkijU+/cCi+BXx+LJftdfFk8oI6mi+ 8nOjwwY3jV2PnJG15RG0NS7KvTFqK30v8ExGFdUcVyHbIgaIhXOv6AUU6OJTbGC7kdLv H/kg== X-Gm-Message-State: AOAM5303MtgmbItawvclJLPNoTRtR7i13NAqz4B35LKvCxKL4q24pR7Q MzE6yXX5Jb7Z+oEMffS9W20= X-Received: by 2002:a2e:3c0c:: with SMTP id j12mr11121695lja.305.1612789370416; Mon, 08 Feb 2021 05:02:50 -0800 (PST) Received: from pc638.lan (h5ef52e3d.seluork.dyn.perspektivbredband.net. [94.245.46.61]) by smtp.gmail.com with ESMTPSA id z15sm2001117lji.110.2021.02.08.05.02.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 05:02:49 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 8 Feb 2021 14:02:48 +0100 To: qiang.zhang@windriver.com Cc: urezki@gmail.com, paulmck@kernel.org, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] kvfree_rcu: Release page cache under memory pressure Message-ID: <20210208130248.GC1920@pc638.lan> References: <20210207124432.10143-1-qiang.zhang@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210207124432.10143-1-qiang.zhang@windriver.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Zqiang. Thank you for your v4! Some small nits see below: > From: Zqiang > > Add free per-cpu existing krcp's page cache operation, when > the system is under memory pressure. > > Signed-off-by: Zqiang > Co-developed-by: Uladzislau Rezki (Sony) > --- > v1->v2->v3->v4: > During the test a page shrinker is pretty active, because of low memory > condition. callback drains it whereas kvfree_rcu() part refill it right > away making kind of vicious circle. > Through Vlad Rezki suggestion, to avoid this, schedule a periodic delayed > work with HZ, and it's easy to do that. > I think the commit message should be improved. Please add a clear description how it works, i mean its connection with shrinker, etc. > kernel/rcu/tree.c | 50 +++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 42 insertions(+), 8 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index c1ae1e52f638..f3b772eef468 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3139,7 +3139,7 @@ struct kfree_rcu_cpu { > bool initialized; > int count; > > - struct work_struct page_cache_work; > + struct delayed_work page_cache_work; > atomic_t work_in_progress; > struct hrtimer hrtimer; > > @@ -3395,7 +3395,7 @@ schedule_page_work_fn(struct hrtimer *t) > struct kfree_rcu_cpu *krcp = > container_of(t, struct kfree_rcu_cpu, hrtimer); > > - queue_work(system_highpri_wq, &krcp->page_cache_work); > + queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0); > return HRTIMER_NORESTART; > } > > @@ -3404,7 +3404,7 @@ static void fill_page_cache_func(struct work_struct *work) > struct kvfree_rcu_bulk_data *bnode; > struct kfree_rcu_cpu *krcp = > container_of(work, struct kfree_rcu_cpu, > - page_cache_work); > + page_cache_work.work); > unsigned long flags; > bool pushed; > int i; > @@ -3428,15 +3428,22 @@ static void fill_page_cache_func(struct work_struct *work) > atomic_set(&krcp->work_in_progress, 0); > } > > +static bool backoff_page_cache_fill; > + > static void > run_page_cache_worker(struct kfree_rcu_cpu *krcp) > { > if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && > !atomic_xchg(&krcp->work_in_progress, 1)) { > - hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, > - HRTIMER_MODE_REL); > - krcp->hrtimer.function = schedule_page_work_fn; > - hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL); > + if (READ_ONCE(backoff_page_cache_fill)) { Can we just use xchg directly inside "if" statement? So we can get rid of below WRITE_ONCE(). It is not considered as a "hot" path, so it should not be an issue. > + queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, HZ); > + WRITE_ONCE(backoff_page_cache_fill, false); > + } else { > + hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, > + HRTIMER_MODE_REL); > + krcp->hrtimer.function = schedule_page_work_fn; > + hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL); > + } > } > } Thank you! -- Vlad Rezki