在 2024/6/4 下午8:01, Baolin Wang 写道:
Cc Johannes, Zi and Vlastimil. On 2024/6/4 17:14, yangge1116@xxxxxxx wrote:From: yangge <yangge1116@xxxxxxx> Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations") no longer differentiates the migration type of pages in THP-sized PCP list, it's possible to get a CMA page from the list, in some cases, it's not acceptable, for example, allocating a non-CMA page with PF_MEMALLOC_PIN flag returns a CMA page. The patch forbids allocating non-CMA THP-sized page from THP-sized PCP list to avoid the issue above.Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations")Signed-off-by: yangge <yangge1116@xxxxxxx> --- mm/page_alloc.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2e22ce5..0bdf471 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2987,10 +2987,20 @@ struct page *rmqueue(struct zone *preferred_zone, WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); if (likely(pcp_allowed_order(order))) { +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA || + order != HPAGE_PMD_ORDER) {Seems you will also miss the non-CMA THP from the PCP, so I wonder if we can add a migratetype comparison in __rmqueue_pcplist(), and if it's not suitable, then fallback to buddy?
Yes, we may miss some non-CMA THPs in the PCP. But, if add a migratetype comparison in __rmqueue_pcplist(), we may need to compare many times because of pcp batch.
