Messages in this thread | | | Date | Wed, 10 Apr 2013 11:20:10 +0800 | From | Simon Jeons <> | Subject | Re: [PATCH 2/3] mm, slub: count freed pages via rcu as this task's reclaimed_slab |
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Hi Christoph, On 04/09/2013 10:32 PM, Christoph Lameter wrote: > On Tue, 9 Apr 2013, Simon Jeons wrote: > >>> + int pages = 1 << compound_order(page); >> One question irrelevant this patch. Why slab cache can use compound >> page(hugetlbfs pages/thp pages)? They are just used by app to optimize tlb >> miss, is it? > Slab caches can use any order pages because these pages are never on > the LRU and are not part of the page cache. Large continuous physical > memory means that objects can be arranged in a more efficient way in the > page. This is particularly useful for larger objects where we might use a > lot of memory because objects do not fit well into a 4k page. > > It also reduces the slab page management if higher order pages are used. > In the case of slub the page size also determines the number of objects > that can be allocated/freed without the need for some form of > synchronization.
It seems that you misunderstand my question. I don't doubt slab/slub can use high order pages. However, what I focus on is why slab/slub can use compound page, PageCompound() just on behalf of hugetlbfs pages or thp pages which should used by apps, isn't it?
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