On 2024/4/4 18:03, Vlastimil Babka wrote:
On 4/3/24 3:47 PM, Baolin Wang wrote:Commit 44042b449872 ("mm/page_alloc: allow high-order pages to be stored on the per-cpu lists") extends the PCP allocator to store THP pages, and it determines whether to cache THP pags in PCP by comparing with pageblock_order. But the pageblock_order is not always equal to THP order, it might also be MAX_PAGE_ORDER, which could prevent PCP from caching THP pages. Therefore, using HPAGE_PMD_ORDER instead to determine the need for caching THP for PCP can fix this issue Fixes: 44042b449872 ("mm/page_alloc: allow high-order pages to be stored on the per-cpu lists") Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>IIUC this happens with CONFIG_HUGETLB_PAGE disabled because HUGETLBFS is disabled? But THPs are still enabled? I think there might be more of THP
Right, and seems the Powerpc arch will set pageblock_order via set_pageblock_order() when the huge page sizes are variable (not sure if this is always equal to THP order).
Moreover, it still does not make sense to use pageblock_order to indicate a THP page, especially when we already have HPAGE_PMD_ORDER to represent THP.
working suboptimally in that case with pageblock_order being larger (MAX_PAGE_ORDER). In other words, should be rather make pageblock_order itself defined as min_t(unsigned int, HPAGE_PMD_ORDER, MAX_PAGE_ORDER) in case with !CONFIG_HUGETLB_PAGE but THP enabled.
Yes, this makes sense to me (I wonder why this wasn't done before?). I can create a seperate patch to do this, what do you think? Thanks.
