From patchwork Mon Aug 13 14:01:10 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 10564267 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5044E13B4 for ; Mon, 13 Aug 2018 14:01:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3EBC429288 for ; Mon, 13 Aug 2018 14:01:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3261D292AE; Mon, 13 Aug 2018 14:01:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 86A8429288 for ; Mon, 13 Aug 2018 14:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729937AbeHMQnp (ORCPT ); Mon, 13 Aug 2018 12:43:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:60808 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728514AbeHMQno (ORCPT ); Mon, 13 Aug 2018 12:43:44 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id DFD03AF7E; Mon, 13 Aug 2018 14:01:16 +0000 (UTC) From: Juergen Gross To: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-block@vger.kernel.org Cc: konrad.wilk@oracle.com, roger.pau@citrix.com, axboe@kernel.dk, boris.ostrovsky@oracle.com, Juergen Gross Subject: [PATCH v3 1/5] xen/blkback: don't keep persistent grants too long Date: Mon, 13 Aug 2018 16:01:10 +0200 Message-Id: <20180813140114.20126-2-jgross@suse.com> X-Mailer: git-send-email 2.13.7 In-Reply-To: <20180813140114.20126-1-jgross@suse.com> References: <20180813140114.20126-1-jgross@suse.com> MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Persistent grants are allocated until a threshold per ring is being reached. Those grants won't be freed until the ring is being destroyed meaning there will be resources kept busy which might no longer be used. Instead of freeing only persistent grants until the threshold is reached add a timestamp and remove all persistent grants not having been in use for a minute. Signed-off-by: Juergen Gross Reviewed-by: Roger Pau Monné --- V3: make timeout parameter static --- Documentation/ABI/testing/sysfs-driver-xen-blkback | 10 +++ drivers/block/xen-blkback/blkback.c | 88 ++++++++++++---------- drivers/block/xen-blkback/common.h | 8 +- 3 files changed, 60 insertions(+), 46 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback index 8bb43b66eb55..4e7babb3ba1f 100644 --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback @@ -15,3 +15,13 @@ Description: blkback. If the frontend tries to use more than max_persistent_grants, the LRU kicks in and starts removing 5% of max_persistent_grants every 100ms. + +What: /sys/module/xen_blkback/parameters/persistent_grant_unused_seconds +Date: August 2018 +KernelVersion: 4.19 +Contact: Roger Pau Monné +Description: + How long a persistent grant is allowed to remain + allocated without being in use. The time is in + seconds, 0 means indefinitely long. + The default is 60 seconds. diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index b55b245e8052..9eae7b243f68 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -84,6 +84,18 @@ MODULE_PARM_DESC(max_persistent_grants, "Maximum number of grants to map persistently"); /* + * How long a persistent grant is allowed to remain allocated without being in + * 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, + uint, 0644); +MODULE_PARM_DESC(persistent_grant_unused_seconds, + "Time in seconds an unused persistent grant is allowed to " + "remain allocated. Default is 60, 0 means unlimited."); + +/* * Maximum number of rings/queues blkback supports, allow as many queues as there * are CPUs if user has not specified a value. */ @@ -123,6 +135,13 @@ module_param(log_stats, int, 0644); /* Number of free pages to remove on each call to gnttab_free_pages */ #define NUM_BATCH_FREE_PAGES 10 +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); +} + static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page) { unsigned long flags; @@ -278,7 +297,7 @@ static void put_persistent_gnt(struct xen_blkif_ring *ring, { if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) pr_alert_ratelimited("freeing a grant already unused\n"); - set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); + persistent_gnt->last_used = jiffies; clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags); atomic_dec(&ring->persistent_gnt_in_use); } @@ -371,26 +390,26 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) struct persistent_gnt *persistent_gnt; struct rb_node *n; unsigned int num_clean, total; - bool scan_used = false, clean_used = false; + bool scan_used = false; struct rb_root *root; - if (ring->persistent_gnt_c < xen_blkif_max_pgrants || - (ring->persistent_gnt_c == xen_blkif_max_pgrants && - !ring->blkif->vbd.overflow_max_grants)) { - goto out; - } - if (work_busy(&ring->persistent_purge_work)) { pr_alert_ratelimited("Scheduled work from previous purge is still busy, cannot purge list\n"); goto out; } - num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN; - num_clean = ring->persistent_gnt_c - xen_blkif_max_pgrants + num_clean; - num_clean = min(ring->persistent_gnt_c, num_clean); - if ((num_clean == 0) || - (num_clean > (ring->persistent_gnt_c - atomic_read(&ring->persistent_gnt_in_use)))) - goto out; + if (ring->persistent_gnt_c < xen_blkif_max_pgrants || + (ring->persistent_gnt_c == xen_blkif_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 = min(ring->persistent_gnt_c, num_clean); + pr_debug("Going to purge at least %u persistent grants\n", + num_clean); + } /* * At this point, we can assure that there will be no calls @@ -401,9 +420,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) * number of grants. */ - total = num_clean; - - pr_debug("Going to purge %u persistent grants\n", num_clean); + total = 0; BUG_ON(!list_empty(&ring->persistent_purge_list)); root = &ring->persistent_gnts; @@ -412,46 +429,37 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) BUG_ON(persistent_gnt->handle == BLKBACK_INVALID_HANDLE); - if (clean_used) { - clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags); - continue; - } - if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags)) continue; - if (!scan_used && - (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags))) + if (!scan_used && !persistent_gnt_timeout(persistent_gnt)) + continue; + if (scan_used && total >= num_clean) continue; rb_erase(&persistent_gnt->node, root); list_add(&persistent_gnt->remove_node, &ring->persistent_purge_list); - if (--num_clean == 0) - goto finished; + total++; } /* - * If we get here it means we also need to start cleaning + * Check whether we also need to start cleaning * grants that were used since last purge in order to cope * with the requested num */ - if (!scan_used && !clean_used) { - pr_debug("Still missing %u purged frames\n", num_clean); + if (!scan_used && total < num_clean) { + pr_debug("Still missing %u purged frames\n", num_clean - total); scan_used = true; goto purge_list; } -finished: - if (!clean_used) { - pr_debug("Finished scanning for grants to clean, removing used flag\n"); - clean_used = true; - goto purge_list; - } - ring->persistent_gnt_c -= (total - num_clean); - ring->blkif->vbd.overflow_max_grants = 0; + if (total) { + ring->persistent_gnt_c -= total; + ring->blkif->vbd.overflow_max_grants = 0; - /* We can defer this work */ - schedule_work(&ring->persistent_purge_work); - pr_debug("Purged %u/%u\n", (total - num_clean), total); + /* We can defer this work */ + schedule_work(&ring->persistent_purge_work); + pr_debug("Purged %u/%u\n", num_clean, total); + } out: return; diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index ecb35fe8ca8d..7bff72db3b7e 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -234,14 +234,9 @@ struct xen_vbd { struct backend_info; /* Number of available flags */ -#define PERSISTENT_GNT_FLAGS_SIZE 2 +#define PERSISTENT_GNT_FLAGS_SIZE 1 /* This persistent grant is currently in use */ #define PERSISTENT_GNT_ACTIVE 0 -/* - * This persistent grant has been used, this flag is set when we remove the - * PERSISTENT_GNT_ACTIVE, to know that this grant has been used recently. - */ -#define PERSISTENT_GNT_WAS_ACTIVE 1 /* Number of requests that we can fit in a ring */ #define XEN_BLKIF_REQS_PER_PAGE 32 @@ -250,6 +245,7 @@ struct persistent_gnt { struct page *page; grant_ref_t gnt; grant_handle_t handle; + unsigned long last_used; DECLARE_BITMAP(flags, PERSISTENT_GNT_FLAGS_SIZE); struct rb_node node; struct list_head remove_node;