Re: [RFC PATCH 10/12] mm: add the buddy system interface

[Xishi Qiu <qiuxishi@huawei.com>]

On 2015/6/9 15:12, Kamezawa Hiroyuki wrote:

> On 2015/06/04 22:04, Xishi Qiu wrote:
>> Add the buddy system interface for address range mirroring feature.
>> Allocate mirrored pages in MIGRATE_MIRROR list. If there is no mirrored pages
>> left, use other types pages.
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>> ---
>>   mm/page_alloc.c | 40 +++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index d4d2066..0fb55288 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -599,6 +599,26 @@ static inline bool is_mirror_pfn(unsigned long pfn)
>>
>>       return false;
>>   }
>> +
>> +static inline bool change_to_mirror(gfp_t gfp_flags, int high_zoneidx)
>> +{
>> +    /*
>> +     * Do not alloc mirrored memory below 4G, because 0-4G is
>> +     * all mirrored by default, and the list is always empty.
>> +     */
>> +    if (high_zoneidx < ZONE_NORMAL)
>> +        return false;
>> +
>> +    /* Alloc mirrored memory for only kernel */
>> +    if (gfp_flags & __GFP_MIRROR)
>> +        return true;
> 
> GFP_KERNEL itself should imply mirror, I think.
> 

Hi Kame,

How about like this: #define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_MIRROR) ?

Thanks,
Xishi Qiu

>> +
>> +    /* Alloc mirrored memory for both user and kernel */
>> +    if (sysctl_mirrorable)
>> +        return true;
> 
> Reading this, I think this sysctl is not good. The user cannot know what is mirrored
> because memory may not be mirrored until the sysctl is set.
> 
> Thanks,
> -Kame
> 
> 
>> +
>> +    return false;
>> +}
>>   #endif
>>
>>   /*
>> @@ -1796,7 +1816,10 @@ struct page *buffered_rmqueue(struct zone *preferred_zone,
>>               WARN_ON_ONCE(order > 1);
>>           }
>>           spin_lock_irqsave(&zone->lock, flags);
>> -        page = __rmqueue(zone, order, migratetype);
>> +        if (is_migrate_mirror(migratetype))
>> +            page = __rmqueue_smallest(zone, order, migratetype);
>> +        else
>> +            page = __rmqueue(zone, order, migratetype);
>>           spin_unlock(&zone->lock);
>>           if (!page)
>>               goto failed;
>> @@ -2928,6 +2951,11 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>>       if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)
>>           alloc_flags |= ALLOC_CMA;
>>
>> +#ifdef CONFIG_MEMORY_MIRROR
>> +    if (change_to_mirror(gfp_mask, ac.high_zoneidx))
>> +        ac.migratetype = MIGRATE_MIRROR;
>> +#endif
>> +
>>   retry_cpuset:
>>       cpuset_mems_cookie = read_mems_allowed_begin();
>>
>> @@ -2943,9 +2971,19 @@ retry_cpuset:
>>
>>       /* First allocation attempt */
>>       alloc_mask = gfp_mask|__GFP_HARDWALL;
>> +retry:
>>       page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);
>>       if (unlikely(!page)) {
>>           /*
>> +         * If there is no mirrored memory, we will alloc other
>> +         * types memory.
>> +         */
>> +        if (is_migrate_mirror(ac.migratetype)) {
>> +            ac.migratetype = gfpflags_to_migratetype(gfp_mask);
>> +            goto retry;
>> +        }
>> +
>> +        /*
>>            * Runtime PM, block IO and its error handling path
>>            * can deadlock because I/O on the device might not
>>            * complete.
>>
> 
> 
> 
> .
> 



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