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[80.230.25.21]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d63dec295sm27487393f8f.14.2026.04.12.15.50.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Apr 2026 15:50:42 -0700 (PDT) Date: Sun, 12 Apr 2026 18:50:40 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , linux-mm@kvack.org, virtualization@lists.linux.dev, Johannes Weiner , Zi Yan Subject: [PATCH RFC 1/9] mm: page_alloc: propagate PageReported flag across buddy splits Message-ID: References: MIME-Version: 1.0 In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: BabmL7tUmT5OpCVuWF-x2W0AIIk-z7OCj6y3CuNN8wE_1776034243 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 6B310140008 X-Stat-Signature: h1js9kwhy1yjpejd4xbhu8tfee9rngn8 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1776034246-260602 X-HE-Meta: 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 N7np3MaO fzIM88KoAwxSH5FNwlfXRfDIvs9FUMsdaZVqaAO2yRpzGL8I9mK31lNmynv6/K3Sk8bYo1UJFa9VyJTS2zjfAEuWgw2suVx5V9BVKlYfZ6MEZxYIelqcA+9sWu13FXS0T0xx54TOMue1WUcxk9c6bsNLm2tAlrp6dvBiEhRrk8pAeDR+7JOVEGBi9G5WCHVkz5KgB0vE54d4Cj+VwbCuticEULGGtyfrDoJrjA/aaofHfREEVI+MFihde9V5gaeRPcVhSz0CKuT0xlDnB0AzQY1QTsj4hLGV2iP/+4KgV43aqEcj3fB3rRO1McBN2J28aRQAeqQW78ct40CGRjlp/X3jwZi0+FtPxsSvURF2FhpjuJvKeXMAqdJkscQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When a reported free page is split via expand() to satisfy a smaller allocation, the sub-pages placed back on the free lists lose the PageReported flag. This means they will be unnecessarily re-reported to the hypervisor in the next reporting cycle, wasting work. Propagate the PageReported flag to sub-pages during expand() so that they are recognized as already-reported. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- mm/page_alloc.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2d4b6f1a554e..edbb1edf463d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1730,7 +1730,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, * -- nyc */ static inline unsigned int expand(struct zone *zone, struct page *page, int low, - int high, int migratetype) + int high, int migratetype, bool reported) { unsigned int size = 1 << high; unsigned int nr_added = 0; @@ -1752,6 +1752,15 @@ static inline unsigned int expand(struct zone *zone, struct page *page, int low, __add_to_free_list(&page[size], zone, high, migratetype, false); set_buddy_order(&page[size], high); nr_added += size; + + /* + * The parent page has been reported to the host. The + * sub-pages are part of the same reported block, so mark + * them reported too. This avoids re-reporting pages that + * the host already knows about. + */ + if (reported) + __SetPageReported(&page[size]); } return nr_added; @@ -1762,9 +1771,10 @@ static __always_inline void page_del_and_expand(struct zone *zone, int high, int migratetype) { int nr_pages = 1 << high; + bool was_reported = page_reported(page); __del_page_from_free_list(page, zone, high, migratetype); - nr_pages -= expand(zone, page, low, high, migratetype); + nr_pages -= expand(zone, page, low, high, migratetype, was_reported); account_freepages(zone, -nr_pages, migratetype); } @@ -2322,7 +2332,8 @@ try_to_claim_block(struct zone *zone, struct page *page, del_page_from_free_list(page, zone, current_order, block_type); change_pageblock_range(page, current_order, start_type); - nr_added = expand(zone, page, order, current_order, start_type); + nr_added = expand(zone, page, order, current_order, start_type, + false); account_freepages(zone, nr_added, start_type); return page; } -- MST