From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-29.mta0.migadu.com [91.218.175.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8A0F463B74 for ; Mon, 14 Sep 2026 12:32:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.29 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789389134; cv=none; b=H9KtG+cbpbdnvdcRf2GCaMBpA8MYg8Q4JTgs7atJwR5/8WXRvV2X4AixfBUnOrOZFSTikXcONxEDc6/UQTalPYvTJZae2zrDZhZ20xqIT7G2CnWBZzcynYIoiPCPwKACvgZq93gr+rFSZH11gMZS6bVkOOQVKAT346HTUSqt880= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789389134; c=relaxed/simple; bh=m4azhIZnpKty8kdqDwfR1PkRU+4t+lf/1EC6ZF7XDMc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e3E5t1j8aXD902T7DAkafCK6KVnkjLI9zpfp0GF+/Sr7xDix91rXf793Qr9Csx9COB9sWBUDNZbuB/AUIUaNLvcJnGroAp+b+1J4bU+3xnwCHTmsrb0dMxoXGGKnvypY/++lobB/G5O4nUWHKms0TM9/BE0U7r287NSq6loBxrQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=SYhMEomT; arc=none smtp.client-ip=91.218.175.29 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="SYhMEomT" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=m4azhIZnpKty8kdqDwfR1PkRU+4t+lf/1EC6ZF7XDMc=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789389123; v=1; x=1789993923; b=SYhMEomTiM1mkK5PkCE1gEHXoIWv4ccLvr3evYTTgNpXZgPsXtetQGlyNh3V+woWnFHO3mKR PAj3JsteRxOGIZ6X19X5oi4uQz6PQOdLERZ2HO1QOkbTL+PEsGXvxsB/FKMfgqq5dMG4P+p3cii yAZ5Oi5hTHhYkkCgqQu6S87A= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta11.migadu.com with ESMTPS id 25c92a897014d0e5; Mon, 14 Sep 2026 12:32:02 +0000 X-Mizu-Trace-ID: 25c92a897014d0e5 X-Migadu-Flow: FLOW_OUT From: Usama Arif To: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , Liam R. Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif Subject: [RESEND v7 23/29] mm/khugepaged: treat PMD swap entries as mapped THPs Date: Mon, 14 Sep 2026 05:28:13 -0700 Message-ID: <20260914122950.3283997-24-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914122950.3283997-1-usama.arif@linux.dev> References: <20260914122950.3283997-1-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit check_pmd_state() would report a PMD swap entry as SCAN_NO_PTE_TABLE - it is not present and, on x86, is also pmd_bad(). The range is already a THP; it just happens to be on disk. Return SCAN_PMD_MAPPED next to the existing migration-entry case and before the pmd_present() and pmd_bad() tests. This does change MADV_COLLAPSE. Today a swapped-out THP is HPAGE_PMD_NR PTE swap entries and MADV_COLLAPSE, which ignores khugepaged_max_ptes_swap, swaps them all in. With a PMD swap entry it reports SCAN_PMD_MAPPED, which madvise_collapse() counts as success, so the call returns 0 without making the range resident. It still faults back in as a whole THP on first touch; only the point at which the I/O happens moves. Signed-off-by: Usama Arif --- mm/khugepaged.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 0d8cd44b14c57..bbbf96c616295 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1052,6 +1052,12 @@ static inline enum scan_result check_pmd_state(pmd_t *pmd) */ if (pmd_is_migration_entry(pmde)) return SCAN_PMD_MAPPED; + /* + * A PMD-mapped THP that has been swapped out is still a THP from + * khugepaged's perspective; treat it like a present huge PMD. + */ + if (pmd_is_swap_entry(pmde)) + return SCAN_PMD_MAPPED; if (!pmd_present(pmde)) return SCAN_NO_PTE_TABLE; if (pmd_trans_huge(pmde)) -- 2.53.0-Meta