Re: [RFC][PATCH 1/2] mm: use MIGRATE_HIGHATOMIC as late as possible

[Xishi Qiu]

On 2017/3/7 18:47, Michal Hocko wrote:

> On Tue 07-03-17 18:33:53, Xishi Qiu wrote:
>> MIGRATE_HIGHATOMIC page blocks are reserved for an atomic
>> high-order allocation, so use it as late as possible.
> 
> Why is this better? Are you seeing any problem which this patch
> resolves? In other words the patch description should explain why not
> only what (that is usually clear from looking at the diff).
> 

Hi Michal,

I have not see any problem yet, I think if we reserve more high order
pageblocks, the more success rate we will get when meet an atomic
high-order allocation, right?

Thanks,
Xishi Qiu

>> Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
>> ---
>>  mm/page_alloc.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 40d79a6..2331840 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2714,14 +2714,12 @@ struct page *rmqueue(struct zone *preferred_zone,
>>  	spin_lock_irqsave(&zone->lock, flags);
>>  
>>  	do {
>> -		page = NULL;
>> -		if (alloc_flags & ALLOC_HARDER) {
>> +		page = __rmqueue(zone, order, migratetype);
>> +		if (!page && alloc_flags & ALLOC_HARDER) {
>>  			page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
>>  			if (page)
>>  				trace_mm_page_alloc_zone_locked(page, order, migratetype);
>>  		}
>> -		if (!page)
>> -			page = __rmqueue(zone, order, migratetype);
>>  	} while (page && check_new_pages(page, order));
>>  	spin_unlock(&zone->lock);
>>  	if (!page)
>> -- 
>> 1.8.3.1
>>
>