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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1931C2D0BE for ; Tue, 10 Dec 2019 06:11:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1AA0206D5 for ; Tue, 10 Dec 2019 06:11:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727063AbfLJGL4 (ORCPT ); Tue, 10 Dec 2019 01:11:56 -0500 Received: from mx2.suse.de ([195.135.220.15]:58028 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725942AbfLJGL4 (ORCPT ); Tue, 10 Dec 2019 01:11:56 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 56FF1B311; Tue, 10 Dec 2019 06:11:53 +0000 (UTC) Subject: Re: [PATCH v4 1/2] xenbus/backend: Add memory pressure handler callback To: SeongJae Park Cc: axboe@kernel.dk, konrad.wilk@oracle.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, pdurrant@amazon.com, roger.pau@citrix.com, sj38.park@gmail.com, xen-devel@lists.xenproject.org, SeongJae Park References: <20191209194305.20828-1-sjpark@amazon.com> <20191209194305.20828-2-sjpark@amazon.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <2aca11d5-38ba-e924-c38e-e48c52c915c6@suse.com> Date: Tue, 10 Dec 2019 07:11:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 MIME-Version: 1.0 In-Reply-To: <20191209194305.20828-2-sjpark@amazon.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.12.19 20:43, SeongJae Park wrote: > From: SeongJae Park > > Granting pages consumes backend system memory. In systems configured > with insufficient spare memory for those pages, it can cause a memory > pressure situation. However, finding the optimal amount of the spare > memory is challenging for large systems having dynamic resource > utilization patterns. Also, such a static configuration might lacks a > flexibility. > > To mitigate such problems, this commit adds a memory reclaim callback to > 'xenbus_driver'. Using this facility, 'xenbus' would be able to monitor > a memory pressure and request specific domains of specific backend > drivers which causing the given pressure to voluntarily release its > memory. > > That said, this commit simply requests every callback registered driver > to release its memory for every domain, rather than issueing the > requests to the drivers and domain in charge. Such things would be a > future work. Also, this commit focuses on memory only. However, it > would be ablt to be extended for general resources. > > Signed-off-by: SeongJae Park > --- > drivers/xen/xenbus/xenbus_probe_backend.c | 31 +++++++++++++++++++++++ > include/xen/xenbus.h | 1 + > 2 files changed, 32 insertions(+) > > diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c > index b0bed4faf44c..cd5fd1cd8de3 100644 > --- a/drivers/xen/xenbus/xenbus_probe_backend.c > +++ b/drivers/xen/xenbus/xenbus_probe_backend.c > @@ -248,6 +248,34 @@ static int backend_probe_and_watch(struct notifier_block *notifier, > return NOTIFY_DONE; > } > > +static int xenbus_backend_reclaim(struct device *dev, void *data) > +{ > + struct xenbus_driver *drv; > + if (!dev->driver) > + return -ENOENT; > + drv = to_xenbus_driver(dev->driver); > + if (drv && drv->reclaim) > + drv->reclaim(to_xenbus_device(dev), DOMID_INVALID); > + return 0; > +} > + > +/* > + * Returns 0 always because we are using shrinker to only detect memory > + * pressure. > + */ > +static unsigned long xenbus_backend_shrink_count(struct shrinker *shrinker, > + struct shrink_control *sc) > +{ > + bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, > + xenbus_backend_reclaim); > + return 0; > +} > + > +static struct shrinker xenbus_backend_shrinker = { > + .count_objects = xenbus_backend_shrink_count, > + .seeks = DEFAULT_SEEKS, > +}; > + > static int __init xenbus_probe_backend_init(void) > { > static struct notifier_block xenstore_notifier = { > @@ -264,6 +292,9 @@ static int __init xenbus_probe_backend_init(void) > > register_xenstore_notifier(&xenstore_notifier); > > + if (register_shrinker(&xenbus_backend_shrinker)) > + pr_warn("shrinker registration failed\n"); > + > return 0; > } > subsys_initcall(xenbus_probe_backend_init); > diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h > index 869c816d5f8c..52aaf4f78400 100644 > --- a/include/xen/xenbus.h > +++ b/include/xen/xenbus.h > @@ -104,6 +104,7 @@ struct xenbus_driver { > struct device_driver driver; > int (*read_otherend_details)(struct xenbus_device *dev); > int (*is_ready)(struct xenbus_device *dev); > + unsigned (*reclaim)(struct xenbus_device *dev, domid_t domid); Can you please add a comment here regarding semantics of specifying DOMID_INVALID as domid? Block maintainers, would you be fine with me carrying this series through the Xen tree? Juergen