Re: [PATCH 3/4] mm/hotplug: free zone->pageset when a zone becomes empty

[Jiang Liu <jiang.liu@huawei.com>]

Hi Bob,
	Yes, we need to handle the wait table too. We has tried to remove the
pgdat and wait table altogether, but found it's really hard to remove pgdat
for empty nodes. I think the candidate solution is to free wait table but
keep pgdat. Any suggestions?
	Thanks!
	Gerry

On 2012-7-19 15:58, Bob Liu wrote:
> On Thu, Jul 5, 2012 at 5:45 PM, Jiang Liu <jiang.liu@huawei.com> wrote:
>> When a zone becomes empty after memory offlining, free zone->pageset.
>> Otherwise it will cause memory leak when adding memory to the empty
>> zone again because build_all_zonelists() will allocate zone->pageset
>> for an empty zone.
>>
> 
> What about other area allocated to the zone?  eg. wait_table?
> 
>> Signed-off-by: Jiang Liu <liuj97@gmail.com>
>> Signed-off-by: Wei Wang <Bessel.Wang@huawei.com>
>> ---
>>  include/linux/mm.h  |    1 +
>>  mm/memory_hotplug.c |    3 +++
>>  mm/page_alloc.c     |   13 +++++++++++++
>>  3 files changed, 17 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index b36d08c..f8b62f2 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1331,6 +1331,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>>  extern void setup_per_cpu_pageset(void);
>>
>>  extern void zone_pcp_update(struct zone *zone);
>> +extern void zone_pcp_reset(struct zone *zone);
>>
>>  /* nommu.c */
>>  extern atomic_long_t mmap_pages_allocated;
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index bce80c7..998b792 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -966,6 +966,9 @@ repeat:
>>
>>         init_per_zone_wmark_min();
>>
>> +       if (!populated_zone(zone))
>> +               zone_pcp_reset(zone);
>> +
>>         if (!node_present_pages(node)) {
>>                 node_clear_state(node, N_HIGH_MEMORY);
>>                 kswapd_stop(node);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index ebf319d..5964b7a 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -5872,6 +5872,19 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
>>  #endif
>>
>>  #ifdef CONFIG_MEMORY_HOTREMOVE
>> +void zone_pcp_reset(struct zone *zone)
>> +{
>> +       unsigned long flags;
>> +
>> +       /* avoid races with drain_pages()  */
>> +       local_irq_save(flags);
>> +       if (zone->pageset != &boot_pageset) {
>> +               free_percpu(zone->pageset);
>> +               zone->pageset = &boot_pageset;
>> +       }
>> +       local_irq_restore(flags);
>> +}
>> +
>>  /*
>>   * All pages in the range must be isolated before calling this.
>>   */
>> --
>> 1.7.1
>>
>>
>> --
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> 
> 
> 


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