From patchwork Wed Dec 18 10:42:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11300235 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 B3431921 for ; Wed, 18 Dec 2019 10:43:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 900E521D7D for ; Wed, 18 Dec 2019 10:43:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="OVC+/1R+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726682AbfLRKnP (ORCPT ); Wed, 18 Dec 2019 05:43:15 -0500 Received: from smtp-fw-4101.amazon.com ([72.21.198.25]:13741 "EHLO smtp-fw-4101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725828AbfLRKnO (ORCPT ); Wed, 18 Dec 2019 05:43:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1576665795; x=1608201795; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=6HH7PeknGCYANJeR4Z4A5j/5EdY1wACfauzPdOr50Ks=; b=OVC+/1R+L/cE8Gwo68YAf2MqJEMkeN2/iRyS8YYXwyQ+dQ7naR/4UD22 gisfpXH2QYDQ95C2T6JCtK+Dn/scXYEjFqmNGtlYm9jF1fZtYoU/Bdjb1 DbcSp1JXGhLMounzV058DivaDuXtkzJcQe0Oj/SqEoO6+ypGYW7Xhj+jJ g=; IronPort-SDR: pXXPpQ94o2PFanZfgkiArLRqYLmZkSnUZR3A0k0zOjAILvvqJwc8x1LGVVKpBklOSrhgpzilPi r0GyC4ycayFg== X-IronPort-AV: E=Sophos;i="5.69,329,1571702400"; d="scan'208";a="9016324" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-2a-22cc717f.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-out-4101.iad4.amazon.com with ESMTP; 18 Dec 2019 10:43:12 +0000 Received: from EX13MTAUEA001.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan3.pdx.amazon.com [10.170.41.166]) by email-inbound-relay-2a-22cc717f.us-west-2.amazon.com (Postfix) with ESMTPS id F198FA25BC; Wed, 18 Dec 2019 10:43:10 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA001.ant.amazon.com (10.43.61.243) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:10 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.100) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:05 +0000 From: SeongJae Park To: , , , CC: SeongJae Park , , , , , , Subject: [PATCH v12 1/5] xenbus/backend: Add memory pressure handler callback Date: Wed, 18 Dec 2019 11:42:28 +0100 Message-ID: <20191218104232.9606-2-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191218104232.9606-1-sjpark@amazon.com> References: <20191218104232.9606-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.160.100] X-ClientProxiedBy: EX13D18UWA003.ant.amazon.com (10.43.160.238) 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 b0bed4faf44c..7e78ebef7c54 100644 --- a/drivers/xen/xenbus/xenbus_probe_backend.c +++ b/drivers/xen/xenbus/xenbus_probe_backend.c @@ -248,6 +248,35 @@ 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 = { @@ -264,6 +293,9 @@ 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 869c816d5f8c..c861cfb6f720 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); + void (*reclaim_memory)(struct xenbus_device *dev); }; static inline struct xenbus_driver *to_xenbus_driver(struct device_driver *drv) From patchwork Wed Dec 18 10:42:29 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11300237 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 6BC66921 for ; Wed, 18 Dec 2019 10:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4921C227BF for ; Wed, 18 Dec 2019 10:43:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="Myon/dg+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726752AbfLRKnd (ORCPT ); Wed, 18 Dec 2019 05:43:33 -0500 Received: from smtp-fw-9101.amazon.com ([207.171.184.25]:21363 "EHLO smtp-fw-9101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725828AbfLRKnd (ORCPT ); Wed, 18 Dec 2019 05:43:33 -0500 DKIM-Signature: v=1; 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Wed, 18 Dec 2019 10:43:20 +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; Wed, 18 Dec 2019 10:43:20 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.100) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:15 +0000 From: SeongJae Park To: , , , CC: SeongJae Park , , , , , , Subject: [PATCH v12 2/5] xenbus/backend: Protect xenbus callback with lock Date: Wed, 18 Dec 2019 11:42:29 +0100 Message-ID: <20191218104232.9606-3-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191218104232.9606-1-sjpark@amazon.com> References: <20191218104232.9606-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.160.100] X-ClientProxiedBy: EX13D18UWA003.ant.amazon.com (10.43.160.238) 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 'reclaim_memory' callback can race with a driver code as this callback will be called from any memory pressure detected context. To deal with the case, this commit adds a spinlock in the 'xenbus_device'. Whenever 'reclaim_memory' callback is called, the lock of the device which passed to the callback as its argument is locked. Thus, drivers registering their 'reclaim_memory' callback should protect the data that might race with the callback with the lock by themselves. Signed-off-by: SeongJae Park --- drivers/xen/xenbus/xenbus_probe.c | 1 + drivers/xen/xenbus/xenbus_probe_backend.c | 11 +++++++++-- include/xen/xenbus.h | 2 ++ 3 files changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 5b471889d723..b86393f172e6 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -472,6 +472,7 @@ int xenbus_probe_node(struct xen_bus_type *bus, goto fail; dev_set_name(&xendev->dev, "%s", devname); + spin_lock_init(&xendev->reclaim_lock); /* Register with generic device framework. */ err = device_register(&xendev->dev); diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c index 7e78ebef7c54..e862cb932cc4 100644 --- a/drivers/xen/xenbus/xenbus_probe_backend.c +++ b/drivers/xen/xenbus/xenbus_probe_backend.c @@ -251,12 +251,19 @@ static int backend_probe_and_watch(struct notifier_block *notifier, static int backend_reclaim_memory(struct device *dev, void *data) { const struct xenbus_driver *drv; + struct xenbus_device *xdev; + unsigned long flags; if (!dev->driver) return 0; drv = to_xenbus_driver(dev->driver); - if (drv && drv->reclaim_memory) - drv->reclaim_memory(to_xenbus_device(dev)); + if (drv && drv->reclaim_memory) { + xdev = to_xenbus_device(dev); + if (!spin_trylock_irqsave(&xdev->reclaim_lock, flags)) + return 0; + drv->reclaim_memory(xdev); + spin_unlock_irqrestore(&xdev->reclaim_lock, flags); + } return 0; } diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index c861cfb6f720..d9468313061d 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -76,6 +76,8 @@ struct xenbus_device { enum xenbus_state state; struct completion down; struct work_struct work; + /* 'reclaim_memory' callback is called while this lock is acquired */ + spinlock_t reclaim_lock; }; static inline struct xenbus_device *to_xenbus_device(struct device *dev) From patchwork Wed Dec 18 10:42:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11300239 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 B35F8921 for ; 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IronPort-SDR: +0plPABqRXJ0aNRkbxV67LZRJBe5YEQmSZQ6Kwt4MDKlYj5S3EfBJrnoac6cx/QzH2f/cM8kqo qEdWeXDp210w== X-IronPort-AV: E=Sophos;i="5.69,329,1571702400"; d="scan'208";a="15600537" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-2c-1968f9fa.us-west-2.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-33001.sea14.amazon.com with ESMTP; 18 Dec 2019 10:43:30 +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-1968f9fa.us-west-2.amazon.com (Postfix) with ESMTPS id 5856DA204D; Wed, 18 Dec 2019 10:43:29 +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; Wed, 18 Dec 2019 10:43:28 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.100) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:23 +0000 From: SeongJae Park To: , , , CC: SeongJae Park , , , , , , Subject: [PATCH v12 3/5] xen/blkback: Squeeze page pools if a memory pressure is detected Date: Wed, 18 Dec 2019 11:42:30 +0100 Message-ID: <20191218104232.9606-4-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191218104232.9606-1-sjpark@amazon.com> References: <20191218104232.9606-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.160.100] X-ClientProxiedBy: EX13D18UWA003.ant.amazon.com (10.43.160.238) 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 Each `blkif` has a free pages pool for the grant mapping. The size of the pool starts from zero and is increased on demand while processing the I/O requests. If current I/O requests handling is finished or 100 milliseconds has passed since last I/O requests handling, it checks and shrinks the pool to not exceed the size limit, `max_buffer_pages`. Therefore, host administrators can cause memory pressure in blkback by attaching a large number of block devices and inducing I/O. Such problematic situations can be avoided by limiting the maximum number of devices that can be attached, but finding the optimal limit is not so easy. Improper set of the limit can results in memory pressure or a resource underutilization. This commit avoids such problematic situations by squeezing the pools (returns every free page in the pool to the system) for a while (users can set this duration via a module parameter) if memory pressure is detected. Discussions =========== The `blkback`'s original shrinking mechanism returns only pages in the pool which are not currently be used by `blkback` to the system. In other words, the pages that are not mapped with granted pages. Because this commit is changing only the shrink limit but still uses the same freeing mechanism it does not touch pages which are currently mapping grants. Once memory pressure is detected, this commit keeps the squeezing limit for a user-specified time duration. The duration should be neither too long nor too short. If it is too long, the squeezing incurring overhead can reduce the I/O performance. If it is too short, `blkback` will not free enough pages to reduce the memory pressure. This commit sets the value as `10 milliseconds` by default because it is a short time in terms of I/O while it is a long time in terms of memory operations. Also, as the original shrinking mechanism works for at least every 100 milliseconds, this could be a somewhat reasonable choice. I also tested other durations (refer to the below section for more details) and confirmed that 10 milliseconds is the one that works best with the test. That said, the proper duration depends on actual configurations and workloads. That's why this commit allows users to set the duration as a module parameter. Memory Pressure Test ==================== To show how this commit fixes the memory pressure situation well, I configured a test environment on a xen-running virtualization system. On the `blkfront` running guest instances, I attach a large number of network-backed volume devices and induce I/O to those. Meanwhile, I measure the number of pages that swapped in (pswpin) and out (pswpout) on the `blkback` running guest. The test ran twice, once for the `blkback` before this commit and once for that after this commit. As shown below, this commit has dramatically reduced the memory pressure: pswpin pswpout before 76,672 185,799 after 867 3,967 Optimal Aggressive Shrinking Duration ------------------------------------- To find a best squeezing duration, I repeated the test with three different durations (1ms, 10ms, and 100ms). The results are as below: duration pswpin pswpout 1 707 5,095 10 867 3,967 100 362 3,348 As expected, the memory pressure decreases as the duration increases, but the reduction become slow from the `10ms`. Based on this results, I chose the default duration as 10ms. Performance Overhead Test ========================= This commit could incur I/O performance degradation under severe memory pressure because the squeezing will require more page allocations per I/O. To show the overhead, I artificially made a worst-case squeezing situation and measured the I/O performance of a `blkfront` running guest. For the artificial squeezing, I set the `blkback.max_buffer_pages` using the `/sys/module/xen_blkback/parameters/max_buffer_pages` file. In this test, I set the value to `1024` and `0`. The `1024` is the default value. Setting the value as `0` is same to a situation doing the squeezing always (worst-case). If the underlying block device is slow enough, the squeezing overhead could be hidden. For the reason, I use a fast block device, namely the rbd[1]: # xl block-attach guest phy:/dev/ram0 xvdb w For the I/O performance measurement, I run a simple `dd` command 5 times directly to the device as below and collect the 'MB/s' results. $ for i in {1..5}; do dd if=/dev/zero of=/dev/xvdb \ bs=4k count=$((256*512)); sync; done The results are as below. 'max_pgs' represents the value of the `blkback.max_buffer_pages` parameter. max_pgs Min Max Median Avg Stddev 0 417 423 420 419.4 2.5099801 1024 414 425 416 417.8 4.4384682 No difference proven at 95.0% confidence In short, even worst case squeezing on ramdisk based fast block device makes no visible performance degradation. Please note that this is just a very simple and minimal test. On systems using super-fast block devices and a special I/O workload, the results might be different. If you have any doubt, test on your machine with your workload to find the optimal squeezing duration for you. [1] https://www.kernel.org/doc/html/latest/admin-guide/blockdev/ramdisk.html Signed-off-by: SeongJae Park --- .../ABI/testing/sysfs-driver-xen-blkback | 10 ++++++ drivers/block/xen-blkback/blkback.c | 7 ++-- drivers/block/xen-blkback/common.h | 1 + drivers/block/xen-blkback/xenbus.c | 32 ++++++++++++++++++- 4 files changed, 47 insertions(+), 3 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback index 4e7babb3ba1f..f01224231f3f 100644 --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback @@ -25,3 +25,13 @@ Description: allocated without being in use. The time is in seconds, 0 means indefinitely long. The default is 60 seconds. + +What: /sys/module/xen_blkback/parameters/buffer_squeeze_duration_ms +Date: December 2019 +KernelVersion: 5.5 +Contact: SeongJae Park +Description: + When memory pressure is reported to blkback this option + controls the duration in milliseconds that blkback will not + cache any page not backed by a grant mapping. + The default is 10ms. diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index fd1e19f1a49f..79f677aeb5cc 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -656,8 +656,11 @@ int xen_blkif_schedule(void *arg) ring->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL); } - /* Shrink if we have more than xen_blkif_max_buffer_pages */ - shrink_free_pagepool(ring, xen_blkif_max_buffer_pages); + /* Shrink the free pages pool if it is too large. */ + if (time_before(jiffies, blkif->buffer_squeeze_end)) + shrink_free_pagepool(ring, 0); + else + shrink_free_pagepool(ring, xen_blkif_max_buffer_pages); if (log_stats && time_after(jiffies, ring->st_print)) print_stats(ring); diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 1d3002d773f7..536c84f61fed 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -319,6 +319,7 @@ struct xen_blkif { /* All rings for this device. */ struct xen_blkif_ring *rings; unsigned int nr_rings; + unsigned long buffer_squeeze_end; }; struct seg_buf { diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index b90dbcd99c03..20045827a391 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -492,6 +492,7 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, static int xen_blkbk_remove(struct xenbus_device *dev) { struct backend_info *be = dev_get_drvdata(&dev->dev); + unsigned long flags; pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id); @@ -504,6 +505,7 @@ static int xen_blkbk_remove(struct xenbus_device *dev) be->backend_watch.node = NULL; } + spin_lock_irqsave(&dev->reclaim_lock, flags); dev_set_drvdata(&dev->dev, NULL); if (be->blkif) { @@ -512,6 +514,7 @@ static int xen_blkbk_remove(struct xenbus_device *dev) /* Put the reference we set in xen_blkif_alloc(). */ xen_blkif_put(be->blkif); } + spin_unlock_irqrestore(&dev->reclaim_lock, flags); return 0; } @@ -597,6 +600,7 @@ static int xen_blkbk_probe(struct xenbus_device *dev, int err; struct backend_info *be = kzalloc(sizeof(struct backend_info), GFP_KERNEL); + unsigned long flags; /* match the pr_debug in xen_blkbk_remove */ pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id); @@ -607,6 +611,7 @@ static int xen_blkbk_probe(struct xenbus_device *dev, return -ENOMEM; } be->dev = dev; + spin_lock_irqsave(&dev->reclaim_lock, flags); dev_set_drvdata(&dev->dev, be); be->blkif = xen_blkif_alloc(dev->otherend_id); @@ -614,8 +619,10 @@ static int xen_blkbk_probe(struct xenbus_device *dev, err = PTR_ERR(be->blkif); be->blkif = NULL; xenbus_dev_fatal(dev, err, "creating block interface"); + spin_unlock_irqrestore(&dev->reclaim_lock, flags); goto fail; } + spin_unlock_irqrestore(&dev->reclaim_lock, flags); err = xenbus_printf(XBT_NIL, dev->nodename, "feature-max-indirect-segments", "%u", @@ -824,6 +831,28 @@ static void frontend_changed(struct xenbus_device *dev, } +/* Once a memory pressure is detected, squeeze free page pools for a while. */ +static unsigned int buffer_squeeze_duration_ms = 10; +module_param_named(buffer_squeeze_duration_ms, + buffer_squeeze_duration_ms, int, 0644); +MODULE_PARM_DESC(buffer_squeeze_duration_ms, +"Duration in ms to squeeze pages buffer when a memory pressure is detected"); + +/* + * Callback received when the memory pressure is detected. + */ +static void reclaim_memory(struct xenbus_device *dev) +{ + struct backend_info *be = dev_get_drvdata(&dev->dev); + + /* Device is registered but not probed yet */ + if (!be) + return; + + be->blkif->buffer_squeeze_end = jiffies + + msecs_to_jiffies(buffer_squeeze_duration_ms); +} + /* ** Connection ** */ @@ -1115,7 +1144,8 @@ static struct xenbus_driver xen_blkbk_driver = { .ids = xen_blkbk_ids, .probe = xen_blkbk_probe, .remove = xen_blkbk_remove, - .otherend_changed = frontend_changed + .otherend_changed = frontend_changed, + .reclaim_memory = reclaim_memory, }; int xen_blkif_xenbus_init(void) From patchwork Wed Dec 18 10:42:31 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11300241 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 EB4A51580 for ; Wed, 18 Dec 2019 10:43:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF2442072B for ; Wed, 18 Dec 2019 10:43:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="BJGEAV1e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726885AbfLRKnt (ORCPT ); Wed, 18 Dec 2019 05:43:49 -0500 Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:10082 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725785AbfLRKns (ORCPT ); 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Wed, 18 Dec 2019 10:43:36 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA001.ant.amazon.com (10.43.61.243) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:35 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.100) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:43:30 +0000 From: SeongJae Park To: , , , CC: SeongJae Park , , , , , , Subject: [PATCH v12 4/5] xen/blkback: Remove unnecessary static variable name prefixes Date: Wed, 18 Dec 2019 11:42:31 +0100 Message-ID: <20191218104232.9606-5-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191218104232.9606-1-sjpark@amazon.com> References: <20191218104232.9606-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.160.100] X-ClientProxiedBy: EX13D18UWA003.ant.amazon.com (10.43.160.238) 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 A few of static variables in blkback have 'xen_blkif_' prefix, though it is unnecessary for static variables. This commit removes such prefixes. Reviewed-by: Roger Pau Monné Signed-off-by: SeongJae Park --- drivers/block/xen-blkback/blkback.c | 37 +++++++++++++---------------- 1 file changed, 17 insertions(+), 20 deletions(-) diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index 79f677aeb5cc..fbd67f8e4e4e 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -62,8 +62,8 @@ * IO workloads. */ -static int xen_blkif_max_buffer_pages = 1024; -module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644); +static int max_buffer_pages = 1024; +module_param_named(max_buffer_pages, max_buffer_pages, int, 0644); MODULE_PARM_DESC(max_buffer_pages, "Maximum number of free pages to keep in each block backend buffer"); @@ -78,8 +78,8 @@ MODULE_PARM_DESC(max_buffer_pages, * algorithm. */ -static int xen_blkif_max_pgrants = 1056; -module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); +static int max_pgrants = 1056; +module_param_named(max_persistent_grants, max_pgrants, int, 0644); MODULE_PARM_DESC(max_persistent_grants, "Maximum number of grants to map persistently"); @@ -88,8 +88,8 @@ MODULE_PARM_DESC(max_persistent_grants, * use. The time is in seconds, 0 means indefinitely long. */ -static unsigned int xen_blkif_pgrant_timeout = 60; -module_param_named(persistent_grant_unused_seconds, xen_blkif_pgrant_timeout, +static unsigned int pgrant_timeout = 60; +module_param_named(persistent_grant_unused_seconds, pgrant_timeout, uint, 0644); MODULE_PARM_DESC(persistent_grant_unused_seconds, "Time in seconds an unused persistent grant is allowed to " @@ -137,9 +137,8 @@ module_param(log_stats, int, 0644); static inline bool persistent_gnt_timeout(struct persistent_gnt *persistent_gnt) { - return xen_blkif_pgrant_timeout && - (jiffies - persistent_gnt->last_used >= - HZ * xen_blkif_pgrant_timeout); + return pgrant_timeout && (jiffies - persistent_gnt->last_used >= + HZ * pgrant_timeout); } static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page) @@ -234,7 +233,7 @@ static int add_persistent_gnt(struct xen_blkif_ring *ring, struct persistent_gnt *this; struct xen_blkif *blkif = ring->blkif; - if (ring->persistent_gnt_c >= xen_blkif_max_pgrants) { + if (ring->persistent_gnt_c >= max_pgrants) { if (!blkif->vbd.overflow_max_grants) blkif->vbd.overflow_max_grants = 1; return -EBUSY; @@ -397,14 +396,13 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) goto out; } - if (ring->persistent_gnt_c < xen_blkif_max_pgrants || - (ring->persistent_gnt_c == xen_blkif_max_pgrants && + if (ring->persistent_gnt_c < max_pgrants || + (ring->persistent_gnt_c == max_pgrants && !ring->blkif->vbd.overflow_max_grants)) { num_clean = 0; } else { - num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; - num_clean = ring->persistent_gnt_c - xen_blkif_max_pgrants + - num_clean; + num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN; + num_clean = ring->persistent_gnt_c - max_pgrants + num_clean; num_clean = min(ring->persistent_gnt_c, num_clean); pr_debug("Going to purge at least %u persistent grants\n", num_clean); @@ -599,8 +597,7 @@ static void print_stats(struct xen_blkif_ring *ring) current->comm, ring->st_oo_req, ring->st_rd_req, ring->st_wr_req, ring->st_f_req, ring->st_ds_req, - ring->persistent_gnt_c, - xen_blkif_max_pgrants); + ring->persistent_gnt_c, max_pgrants); ring->st_print = jiffies + msecs_to_jiffies(10 * 1000); ring->st_rd_req = 0; ring->st_wr_req = 0; @@ -660,7 +657,7 @@ int xen_blkif_schedule(void *arg) if (time_before(jiffies, blkif->buffer_squeeze_end)) shrink_free_pagepool(ring, 0); else - shrink_free_pagepool(ring, xen_blkif_max_buffer_pages); + shrink_free_pagepool(ring, max_buffer_pages); if (log_stats && time_after(jiffies, ring->st_print)) print_stats(ring); @@ -887,7 +884,7 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring, continue; } if (use_persistent_gnts && - ring->persistent_gnt_c < xen_blkif_max_pgrants) { + ring->persistent_gnt_c < max_pgrants) { /* * We are using persistent grants, the grant is * not mapped but we might have room for it. @@ -914,7 +911,7 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring, pages[seg_idx]->persistent_gnt = persistent_gnt; pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n", persistent_gnt->gnt, ring->persistent_gnt_c, - xen_blkif_max_pgrants); + max_pgrants); goto next; } if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) { From patchwork Wed Dec 18 10:44:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11300253 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 E625E1580 for ; Wed, 18 Dec 2019 10:44:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C3939206EC for ; Wed, 18 Dec 2019 10:44:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="Eh5T014k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725930AbfLRKoy (ORCPT ); Wed, 18 Dec 2019 05:44:54 -0500 Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:10241 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725828AbfLRKox (ORCPT ); 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Wed, 18 Dec 2019 10:44:51 +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; Wed, 18 Dec 2019 10:44:51 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.162.83) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Wed, 18 Dec 2019 10:44:46 +0000 From: SeongJae Park To: , , , CC: SeongJae Park , , , , , , Subject: [PATCH v12 5/5] xen/blkback: Consistently insert one empty line between functions Date: Wed, 18 Dec 2019 11:44:28 +0100 Message-ID: <20191218104428.10069-1-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191218104232.9606-1-sjpark@amazon.com> References: <20191218104232.9606-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.162.83] X-ClientProxiedBy: EX13D35UWC001.ant.amazon.com (10.43.162.197) 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 The number of empty lines between functions in the xenbus.c is inconsistent. This trivial style cleanup commit fixes the file to consistently place only one empty line. Acked-by: Roger Pau Monné Signed-off-by: SeongJae Park --- drivers/block/xen-blkback/xenbus.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 20045827a391..453f97dd533d 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -432,7 +432,6 @@ static void xenvbd_sysfs_delif(struct xenbus_device *dev) device_remove_file(&dev->dev, &dev_attr_physical_device); } - static void xen_vbd_free(struct xen_vbd *vbd) { if (vbd->bdev) @@ -489,6 +488,7 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, handle, blkif->domid); return 0; } + static int xen_blkbk_remove(struct xenbus_device *dev) { struct backend_info *be = dev_get_drvdata(&dev->dev); @@ -575,6 +575,7 @@ static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info if (err) dev_warn(&dev->dev, "writing feature-discard (%d)", err); } + int xen_blkbk_barrier(struct xenbus_transaction xbt, struct backend_info *be, int state) { @@ -663,7 +664,6 @@ static int xen_blkbk_probe(struct xenbus_device *dev, return err; } - /* * Callback received when the hotplug scripts have placed the physical-device * node. Read it and the mode node, and create a vbd. If the frontend is @@ -755,7 +755,6 @@ static void backend_changed(struct xenbus_watch *watch, } } - /* * Callback received when the frontend's state changes. */ @@ -830,7 +829,6 @@ static void frontend_changed(struct xenbus_device *dev, } } - /* Once a memory pressure is detected, squeeze free page pools for a while. */ static unsigned int buffer_squeeze_duration_ms = 10; module_param_named(buffer_squeeze_duration_ms, @@ -855,7 +853,6 @@ static void reclaim_memory(struct xenbus_device *dev) /* ** Connection ** */ - /* * Write the physical details regarding the block device to the store, and * switch to Connected state.