Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753629Ab0L2RUT (ORCPT ); Wed, 29 Dec 2010 12:20:19 -0500 Received: from router-fw.net-space.pl ([89.174.63.77]:47397 "EHLO router-fw.net-space.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753518Ab0L2RTd (ORCPT ); Wed, 29 Dec 2010 12:19:33 -0500 Date: Wed, 29 Dec 2010 18:05:41 +0100 From: Daniel Kiper To: ian.campbell@citrix.com, akpm@linux-foundation.org, andi.kleen@intel.com, haicheng.li@linux.intel.com, fengguang.wu@intel.com, jeremy@goop.org, konrad.wilk@oracle.com, dan.magenheimer@oracle.com, v.tolstov@selfip.ru, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH R2 5/7] xen/balloon: Protect before CPU exhaust by event/x process Message-ID: <20101229170541.GJ2743@router-fw-old.local.net-space.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6517 Lines: 233 Protect before CPU exhaust by event/x process during errors by adding some delays in scheduling next event. Signed-off-by: Daniel Kiper --- drivers/xen/balloon.c | 100 ++++++++++++++++++++++++++++++++++++++++--------- 1 files changed, 82 insertions(+), 18 deletions(-) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 11143af..a62427d 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -65,6 +65,20 @@ #define BALLOON_CLASS_NAME "xen_memory" +/* + * balloon_process() state: + * + * BP_ERROR: error, go to sleep, + * BP_DONE: done or nothing to do, + * BP_HUNGRY: hungry. + */ + +enum bp_state { + BP_ERROR, + BP_DONE, + BP_HUNGRY +}; + struct balloon_stats { /* We aim for 'current allocation' == 'target allocation'. */ unsigned long current_pages; @@ -72,6 +86,8 @@ struct balloon_stats { /* Number of pages in high- and low-memory balloons. */ unsigned long balloon_low; unsigned long balloon_high; + unsigned long schedule_delay; + unsigned long max_schedule_delay; }; static DEFINE_MUTEX(balloon_mutex); @@ -166,6 +182,25 @@ static struct page *balloon_next_page(struct page *page) return list_entry(next, struct page, lru); } +static void update_schedule_delay(enum bp_state state) +{ + unsigned long new_schedule_delay; + + if (state != BP_ERROR) { + balloon_stats.schedule_delay = 1; + return; + } + + new_schedule_delay = balloon_stats.schedule_delay << 1; + + if (new_schedule_delay > balloon_stats.max_schedule_delay) { + balloon_stats.schedule_delay = balloon_stats.max_schedule_delay; + return; + } + + balloon_stats.schedule_delay = new_schedule_delay; +} + static unsigned long current_target(void) { unsigned long target = balloon_stats.target_pages; @@ -178,11 +213,12 @@ static unsigned long current_target(void) return target; } -static int increase_reservation(unsigned long nr_pages) +static enum bp_state increase_reservation(unsigned long nr_pages) { + enum bp_state state = BP_DONE; + int rc; unsigned long pfn, i, flags; struct page *page; - long rc; struct xen_memory_reservation reservation = { .address_bits = 0, .extent_order = 0, @@ -195,8 +231,17 @@ static int increase_reservation(unsigned long nr_pages) spin_lock_irqsave(&xen_reservation_lock, flags); page = balloon_first_page(); + + if (!page) { + state = BP_ERROR; + goto out; + } + for (i = 0; i < nr_pages; i++) { - BUG_ON(page == NULL); + if (!page) { + nr_pages = i; + break; + } frame_list[i] = page_to_pfn(page); page = balloon_next_page(page); } @@ -204,8 +249,11 @@ static int increase_reservation(unsigned long nr_pages) set_xen_guest_handle(reservation.extent_start, frame_list); reservation.nr_extents = nr_pages; rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation); - if (rc < 0) - goto out; + if (rc < nr_pages) { + state = (rc <= 0) ? BP_ERROR : BP_HUNGRY; + if (rc <= 0) + goto out; + } for (i = 0; i < rc; i++) { page = balloon_retrieve(); @@ -238,14 +286,14 @@ static int increase_reservation(unsigned long nr_pages) out: spin_unlock_irqrestore(&xen_reservation_lock, flags); - return rc < 0 ? rc : rc != nr_pages; + return state; } -static int decrease_reservation(unsigned long nr_pages) +static enum bp_state decrease_reservation(unsigned long nr_pages) { + enum bp_state state = BP_DONE; unsigned long pfn, i, flags; struct page *page; - int need_sleep = 0; int ret; struct xen_memory_reservation reservation = { .address_bits = 0, @@ -259,7 +307,7 @@ static int decrease_reservation(unsigned long nr_pages) for (i = 0; i < nr_pages; i++) { if ((page = alloc_page(GFP_BALLOON)) == NULL) { nr_pages = i; - need_sleep = 1; + state = BP_ERROR; break; } @@ -299,7 +347,7 @@ static int decrease_reservation(unsigned long nr_pages) spin_unlock_irqrestore(&xen_reservation_lock, flags); - return need_sleep; + return state; } /* @@ -310,27 +358,35 @@ static int decrease_reservation(unsigned long nr_pages) */ static void balloon_process(struct work_struct *work) { - int need_sleep = 0; + enum bp_state rc, state = BP_DONE; long credit; mutex_lock(&balloon_mutex); do { credit = current_target() - balloon_stats.current_pages; - if (credit > 0) - need_sleep = (increase_reservation(credit) != 0); - if (credit < 0) - need_sleep = (decrease_reservation(-credit) != 0); + + if (credit > 0) { + rc = increase_reservation(credit); + state = (rc == BP_ERROR) ? BP_ERROR : state; + } + + if (credit < 0) { + rc = decrease_reservation(-credit); + state = (rc == BP_ERROR) ? BP_ERROR : state; + } + + update_schedule_delay(state); #ifndef CONFIG_PREEMPT if (need_resched()) schedule(); #endif - } while ((credit != 0) && !need_sleep); + } while (credit && state != BP_ERROR); /* Schedule more work if there is some still to be done. */ - if (current_target() != balloon_stats.current_pages) - schedule_delayed_work(&balloon_worker, HZ); + if (state == BP_ERROR) + schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ); mutex_unlock(&balloon_mutex); } @@ -399,6 +455,9 @@ static int __init balloon_init(void) balloon_stats.balloon_low = 0; balloon_stats.balloon_high = 0; + balloon_stats.schedule_delay = 1; + balloon_stats.max_schedule_delay = 32; + register_balloon(&balloon_sysdev); /* Initialise the balloon with excess memory space. */ @@ -439,6 +498,9 @@ BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages)); BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low)); BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high)); +static SYSDEV_ULONG_ATTR(schedule_delay, 0644, balloon_stats.schedule_delay); +static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay); + static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr, char *buf) { @@ -500,6 +562,8 @@ static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR, static struct sysdev_attribute *balloon_attrs[] = { &attr_target_kb, &attr_target, + &attr_schedule_delay.attr, + &attr_max_schedule_delay.attr }; static struct attribute *balloon_info_attrs[] = { -- 1.4.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/