From patchwork Mon Jan 27 08:18:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11352187 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5DDEE159A for ; Mon, 27 Jan 2020 08:19:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C73421D7D for ; Mon, 27 Jan 2020 08:19:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="V78aZ12f" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729054AbgA0IS5 (ORCPT ); Mon, 27 Jan 2020 03:18:57 -0500 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:64710 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729012AbgA0IS4 (ORCPT ); Mon, 27 Jan 2020 03:18:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1580113135; x=1611649135; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=AlgYXHZVMr+gkDp34KurcKlh0X9TRVaRFfmS+SsrAhM=; b=V78aZ12f9RO+kPHCdXUUmBddam2sKVdygpCnR/MmVc69z9JSa7k/Gx3O Oe5fCcuCvUuGHz78VsIfUVUH1rLmdjhoLEZTl/asbQ8W3rkIDPbkb5i7j zDvLuk2SeCr7Oo8K2cgxQHwfp8n/J1jTQpu7FssVPEkRcqpAPfYwra67F w=; IronPort-SDR: uMkQlNiB9w5LHs1zA7FOvJdLJiQC00IV2UorSjll8vNCEJaZKnmwAqbu3FMlvy4oKtfAHCugov 90/hYLNt0awA== X-IronPort-AV: E=Sophos;i="5.70,369,1574121600"; d="scan'208";a="22599795" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-2c-397e131e.us-west-2.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-33001.sea14.amazon.com with ESMTP; 27 Jan 2020 08:18:43 +0000 Received: from EX13MTAUEA002.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan3.pdx.amazon.com [10.170.41.166]) by email-inbound-relay-2c-397e131e.us-west-2.amazon.com (Postfix) with ESMTPS id BBF46A22CE; Mon, 27 Jan 2020 08:18:42 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1236.3; Mon, 27 Jan 2020 08:18:42 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.8) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Mon, 27 Jan 2020 08:18:37 +0000 From: To: , , CC: SeongJae Park , , , , , Subject: [PATCH v14 1/5] xenbus/backend: Add memory pressure handler callback Date: Mon, 27 Jan 2020 09:18:08 +0100 Message-ID: <20200127081812.21216-2-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200127081812.21216-1-sjpark@amazon.com> References: <20200127081812.21216-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.160.8] X-ClientProxiedBy: EX13D11UWB004.ant.amazon.com (10.43.161.90) To EX13D31EUA001.ant.amazon.com (10.43.165.15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 lack flexibility. To mitigate such problems, this commit adds a memory reclaim callback to 'xenbus_driver'. If a memory pressure is detected, 'xenbus' requests every backend driver to volunarily release its memory. Note that it would be able to improve the callback facility for more sophisticated handlings of general pressures. For example, it would be possible to monitor the memory consumption of each device and issue the release requests to only devices which causing the pressure. Also, the callback could be extended to handle not only memory, but general resources. Nevertheless, this version of the implementation defers such sophisticated goals as a future work. Reviewed-by: Juergen Gross Reviewed-by: Roger Pau Monné Signed-off-by: SeongJae Park --- drivers/xen/xenbus/xenbus_probe_backend.c | 32 +++++++++++++++++++++++ include/xen/xenbus.h | 1 + 2 files changed, 33 insertions(+) diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c index 14876faff3b0..3b5cb7a5a7e4 100644 --- a/drivers/xen/xenbus/xenbus_probe_backend.c +++ b/drivers/xen/xenbus/xenbus_probe_backend.c @@ -247,6 +247,35 @@ static int backend_probe_and_watch(struct notifier_block *notifier, return NOTIFY_DONE; } +static int backend_reclaim_memory(struct device *dev, void *data) +{ + const struct xenbus_driver *drv; + + if (!dev->driver) + return 0; + drv = to_xenbus_driver(dev->driver); + if (drv && drv->reclaim_memory) + drv->reclaim_memory(to_xenbus_device(dev)); + return 0; +} + +/* + * Returns 0 always because we are using shrinker to only detect memory + * pressure. + */ +static unsigned long backend_shrink_memory_count(struct shrinker *shrinker, + struct shrink_control *sc) +{ + bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, + backend_reclaim_memory); + return 0; +} + +static struct shrinker backend_memory_shrinker = { + .count_objects = backend_shrink_memory_count, + .seeks = DEFAULT_SEEKS, +}; + static int __init xenbus_probe_backend_init(void) { static struct notifier_block xenstore_notifier = { @@ -263,6 +292,9 @@ static int __init xenbus_probe_backend_init(void) register_xenstore_notifier(&xenstore_notifier); + if (register_shrinker(&backend_memory_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 24228a102141..980952ea452b 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -105,6 +105,7 @@ struct xenbus_driver { struct device_driver driver; int (*read_otherend_details)(struct xenbus_device *dev); int (*is_ready)(struct xenbus_device *dev); + void (*reclaim_memory)(struct xenbus_device *dev); }; static inline struct xenbus_driver *to_xenbus_driver(struct device_driver *drv)