Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933345AbZJIOdz (ORCPT ); Fri, 9 Oct 2009 10:33:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933185AbZJIOdz (ORCPT ); Fri, 9 Oct 2009 10:33:55 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:60761 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932999AbZJIOdy (ORCPT ); Fri, 9 Oct 2009 10:33:54 -0400 Date: Fri, 9 Oct 2009 09:33:01 -0500 From: Robert Jennings To: KAMEZAWA Hiroyuki Cc: Mel Gorman , Ingo Molnar , Badari Pulavarty , Brian King , Benjamin Herrenschmidt , Paul Mackerras , Martin Schwidefsky , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@ozlabs.org Subject: Re: [PATCH 1/2][v2] mm: add notifier in pageblock isolation for balloon drivers Message-ID: <20091009143301.GA11543@austin.ibm.com> Mail-Followup-To: KAMEZAWA Hiroyuki , Mel Gorman , Ingo Molnar , Badari Pulavarty , Brian King , Benjamin Herrenschmidt , Paul Mackerras , Martin Schwidefsky , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@ozlabs.org References: <20091002184458.GC4908@austin.ibm.com> <20091009094740.fe84e46a.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091009094740.fe84e46a.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8437 Lines: 241 * KAMEZAWA Hiroyuki (kamezawa.hiroyu@jp.fujitsu.com) wrote: > On Fri, 2 Oct 2009 13:44:58 -0500 > Robert Jennings wrote: > > > Memory balloon drivers can allocate a large amount of memory which > > is not movable but could be freed to accomodate memory hotplug remove. > > > > Prior to calling the memory hotplug notifier chain the memory in the > > pageblock is isolated. If the migrate type is not MIGRATE_MOVABLE the > > isolation will not proceed, causing the memory removal for that page > > range to fail. > > > > Rather than failing pageblock isolation if the the migrateteype is not > > MIGRATE_MOVABLE, this patch checks if all of the pages in the pageblock > > are owned by a registered balloon driver (or other entity) using a > > notifier chain. If all of the non-movable pages are owned by a balloon, > > they can be freed later through the memory notifier chain and the range > > can still be isolated in set_migratetype_isolate(). > > > > Signed-off-by: Robert Jennings > > > > --- > > drivers/base/memory.c | 19 +++++++++++++++++++ > > include/linux/memory.h | 26 ++++++++++++++++++++++++++ > > mm/page_alloc.c | 45 ++++++++++++++++++++++++++++++++++++++------- > > 3 files changed, 83 insertions(+), 7 deletions(-) > > > > Index: b/drivers/base/memory.c > > =================================================================== > > --- a/drivers/base/memory.c > > +++ b/drivers/base/memory.c > > @@ -63,6 +63,20 @@ void unregister_memory_notifier(struct n > > } > > EXPORT_SYMBOL(unregister_memory_notifier); > > > > +static BLOCKING_NOTIFIER_HEAD(memory_isolate_chain); > > + > > IIUC, this notifier is called under zone->lock. > please ATOMIC_NOTIFIER_HEAD(). I will correct this. > > +int register_memory_isolate_notifier(struct notifier_block *nb) > > +{ > > + return blocking_notifier_chain_register(&memory_isolate_chain, nb); > > +} > > +EXPORT_SYMBOL(register_memory_isolate_notifier); > > + > > +void unregister_memory_isolate_notifier(struct notifier_block *nb) > > +{ > > + blocking_notifier_chain_unregister(&memory_isolate_chain, nb); > > +} > > +EXPORT_SYMBOL(unregister_memory_isolate_notifier); > > + > > /* > > * register_memory - Setup a sysfs device for a memory block > > */ > > @@ -157,6 +171,11 @@ int memory_notify(unsigned long val, voi > > return blocking_notifier_call_chain(&memory_chain, val, v); > > } > > > > +int memory_isolate_notify(unsigned long val, void *v) > > +{ > > + return blocking_notifier_call_chain(&memory_isolate_chain, val, v); > > +} > > + > > /* > > * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is > > * OK to have direct references to sparsemem variables in here. > > Index: b/include/linux/memory.h > > =================================================================== > > --- a/include/linux/memory.h > > +++ b/include/linux/memory.h > > @@ -50,6 +50,18 @@ struct memory_notify { > > int status_change_nid; > > }; > > > > +/* > > + * During pageblock isolation, count the number of pages in the > > + * range [start_pfn, start_pfn + nr_pages) > > + */ > > +#define MEM_ISOLATE_COUNT (1<<0) > > + > > +struct memory_isolate_notify { > > + unsigned long start_pfn; > > + unsigned int nr_pages; > > + unsigned int pages_found; > > +}; > > Could you add commentary for each field ? This will be documented in the next version of the patch. > > + > > struct notifier_block; > > struct mem_section; > > > > @@ -76,14 +88,28 @@ static inline int memory_notify(unsigned > > { > > return 0; > > } > > +static inline int register_memory_isolate_notifier(struct notifier_block *nb) > > +{ > > + return 0; > > +} > > +static inline void unregister_memory_isolate_notifier(struct notifier_block *nb) > > +{ > > +} > > +static inline int memory_isolate_notify(unsigned long val, void *v) > > +{ > > + return 0; > > +} > > #else > > extern int register_memory_notifier(struct notifier_block *nb); > > extern void unregister_memory_notifier(struct notifier_block *nb); > > +extern int register_memory_isolate_notifier(struct notifier_block *nb); > > +extern void unregister_memory_isolate_notifier(struct notifier_block *nb); > > extern int register_new_memory(int, struct mem_section *); > > extern int unregister_memory_section(struct mem_section *); > > extern int memory_dev_init(void); > > extern int remove_memory_block(unsigned long, struct mem_section *, int); > > extern int memory_notify(unsigned long val, void *v); > > +extern int memory_isolate_notify(unsigned long val, void *v); > > extern struct memory_block *find_memory_block(struct mem_section *); > > #define CONFIG_MEM_BLOCK_SIZE (PAGES_PER_SECTION< > enum mem_add_context { BOOT, HOTPLUG }; > > Index: b/mm/page_alloc.c > > =================================================================== > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -48,6 +48,7 @@ > > #include > > #include > > #include > > +#include > > #include > > > > #include > > @@ -4985,23 +4986,53 @@ void set_pageblock_flags_group(struct pa > > int set_migratetype_isolate(struct page *page) > > { > > struct zone *zone; > > - unsigned long flags; > > + unsigned long flags, pfn, iter; > > + unsigned long immobile = 0; > > + struct memory_isolate_notify arg; > > + int notifier_ret; > > int ret = -EBUSY; > > int zone_idx; > > > > zone = page_zone(page); > > zone_idx = zone_idx(zone); > > + > > spin_lock_irqsave(&zone->lock, flags); > > + if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE || > > + zone_idx == ZONE_MOVABLE) { > > + ret = 0; > > + goto out; > > + } > > + > > + pfn = page_to_pfn(page); > > + arg.start_pfn = pfn; > > + arg.nr_pages = pageblock_nr_pages; > > + arg.pages_found = 0; > > + > > /* > > - * In future, more migrate types will be able to be isolation target. > > + * The pageblock can be isolated even if the migrate type is > > + * not *_MOVABLE. The memory isolation notifier chain counts > > + * the number of pages in this pageblock that can be freed later > > + * through the memory notifier chain. If all of the pages are > > + * accounted for, isolation can continue. > > */ > > Could add explanation like this ? > == > Later, for example, when memory hotplug notifier runs, these pages reported as > "can be isoalted" should be isolated(freed) by callbacks. > == I'll change this comment. You and Mel both gave me good direction here. > > - if (get_pageblock_migratetype(page) != MIGRATE_MOVABLE && > > - zone_idx != ZONE_MOVABLE) > > + notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg); > > + notifier_ret = notifier_to_errno(notifier_ret); > > + if (notifier_ret || !arg.pages_found) > > goto out; > > - set_pageblock_migratetype(page, MIGRATE_ISOLATE); > > - move_freepages_block(zone, page, MIGRATE_ISOLATE); > > - ret = 0; > > + > > + for (iter = pfn; iter < (pfn + pageblock_nr_pages); iter++) > > + if (page_count(pfn_to_page(iter))) > > + immobile++; > > + > > + if (arg.pages_found == immobile) > > + ret = 0; > > + > > I can't understand this part. Does this mean all pages under this pageblock > are used by balloon driver ? > IOW, memory is hotpluggable only when all pages under this pageblock is used > by balloon ? > > > Hmm. Can't we do this kind of check..? > == > for (iter = pfn; iter < (pfn + pageblock_nr_pages); iter++) { > page = pfn_to_page(iter); > if (!page_count(page) || PageLRU(page)) // This page is movable. > continue; > immobile++ > } > == > Then, if a page is luckyly on LRU, we have more chances. > (This check can fail if a page is on percpu pagevec etc...) > > Thanks, > -Kame I like this change, it will be in my next patch after I finish testing. Thank you for your review. > > out: > > + if (!ret) { > > + set_pageblock_migratetype(page, MIGRATE_ISOLATE); > > + move_freepages_block(zone, page, MIGRATE_ISOLATE); > > + } > > + > > spin_unlock_irqrestore(&zone->lock, flags); > > if (!ret) > > drain_all_pages(); > > > > -- -- 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/