Re: [Xen-devel] [PATCH RESEND RFC 2/8] mm: Place unscrubbed pages at the end of pagelist

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

>>  
>>  static void merge_chunks(struct page_info *pg, unsigned int node,
>> -                         unsigned int zone, unsigned int order)
>> +                         unsigned int zone, unsigned int order,
>> +                         bool_t need_scrub)
> Can't you calculate need_scrub from *pg rather than passing an extra
> parameter?

Right, I can just look at the head's PGC_need_scrub bit.

>>  {
>>      ASSERT(spin_is_locked(&heap_lock));
>>  
>> @@ -970,12 +982,49 @@ static void merge_chunks(struct page_info *pg, 
>> unsigned int node,
>>      }
>>  
>>      PFN_ORDER(pg) = order;
>> -    page_list_add_tail(pg, &heap(node, zone, order));
>> +    if ( need_scrub )
>> +        page_list_add_tail(pg, &heap(node, zone, order));
>> +    else
>> +        page_list_add(pg, &heap(node, zone, order));
>> +}
>> +
>> +static void scrub_free_pages(unsigned int node)
>> +{
>> +    struct page_info *pg;
>> +    unsigned int i, zone;
>> +    int order;
>> +
>> +    ASSERT(spin_is_locked(&heap_lock));
>> +
>> +    if ( !node_need_scrub[node] )
>> +        return;
>> +
>> +    for ( zone = 0; zone < NR_ZONES; zone++ )
>> +    {
>> +        for ( order = MAX_ORDER; order >= 0; order-- )
>> +        {
>> +            while ( !page_list_empty(&heap(node, zone, order)) )
>> +            {
>> +                /* Unscrubbed pages are always at the end of the list. */
>> +                pg = page_list_last(&heap(node, zone, order));
>> +                if ( !test_bit(_PGC_need_scrub, &pg[0].count_info) )
> &pg->count_info
>
>> +                    break;
>> +
>> +                for ( i = 0; i < (1 << order); i++)
> 1U, and probably unsigned long.  Similarly later.

I'll update sizing throughout the series.

I just noticed, BTW, that this routine lost something like

   page_list_del(pg, &heap(node, zone, order));
   merge_chunks(pg, node, zone, chunk_order, 0);

otherwise we just scrub the last chunk on each list.

This is all rewritten in a later patch which is why I missed this during
testing.

-boris




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