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Date: Tue, 31 May 2022 22:41:12 +0800 From: Chen Lin <chen45464546@....com> To: kuba@...nel.org Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, alexander.duyck@...il.com, netdev@...r.kernel.org, Chen Lin <chen45464546@....com> Subject: Re:Re: [PATCH v2] mm: page_frag: Warn_on when frag_alloc size is bigger than PAGE_SIZE At 2022-05-31 02:29:18, "Jakub Kicinski" <kuba@...nel.org> wrote: >On Mon, 30 May 2022 12:27:05 -0700 Jakub Kicinski wrote: >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index e008a3df0485..360a545ee5e8 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -5537,6 +5537,7 @@ EXPORT_SYMBOL(free_pages); >> * sk_buff->head, or to be used in the "frags" portion of skb_shared_info. >> */ >> static struct page *__page_frag_cache_refill(struct page_frag_cache *nc, >> + unsigned int fragsz, >> gfp_t gfp_mask) >> { >> struct page *page = NULL; >> @@ -5549,7 +5550,7 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc, >> PAGE_FRAG_CACHE_MAX_ORDER); >> nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE; >> #endif >> - if (unlikely(!page)) >> + if (unlikely(!page && fragsz <= PAGE_SIZE)) >> page = alloc_pages_node(NUMA_NO_NODE, gfp, 0); >> >> nc->va = page ? page_address(page) : NULL; >> @@ -5576,7 +5577,7 @@ void *page_frag_alloc_align(struct page_frag_cache *nc, >> >> if (unlikely(!nc->va)) { >> refill: >> - page = __page_frag_cache_refill(nc, gfp_mask); >> + page = __page_frag_cache_refill(nc, fragsz, gfp_mask); >> if (!page) >> return NULL; > >Oh, well, the reuse also needs an update. We can slap a similar >condition next to the pfmemalloc check. The sample code above cannot completely solve the current problem. For example, when fragsz is greater than PAGE_FRAG_CACHE_MAX_SIZE(32768), __page_frag_cache_refill will return a memory of only 32768 bytes, so should we continue to expand the PAGE_FRAG_CACHE_MAX_SIZE? Maybe more work needs to be done
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