From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-207.mta1.migadu.com [95.215.58.207]) (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 46F9747F2CC for ; Fri, 2 Oct 2026 09:57:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.207 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935045; cv=none; b=EpdJdgC9+bEOIhRQRbcTf8N4lMusLCjDkz/x76NxDTCyoPcXDv6X0EqevQuOKuMXZwpa97UjtDr1FlIfwrgrX7MZ2Bc0samfuQcQH7R/yJYMoI6SwVWAuFd7n2DI5asFidcGuSAcNNPVd6+7pAYWzj8Nf7HUmCLk4Ip4YDGqwKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935045; c=relaxed/simple; bh=m4azhIZnpKty8kdqDwfR1PkRU+4t+lf/1EC6ZF7XDMc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QPwr9bGVH9zDlcVYGuczz+j9gkzA3TlHY07FB5FOTwOF6Tl2Ygv33xBdetkgyGSFtvCH3mlLlZaIMNBoNQXOng5hJqWkW9FwduL+Q2scmgw5XmktFBtZHoVBEvm1vugS2HUhH7yg/bz1nzR36BVw7hiqSVMBE4L1ztBpxM2360M= 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=PGQXu12m; arc=none smtp.client-ip=95.215.58.207 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="PGQXu12m" 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=1790935042; v=1; x=1791539842; b=PGQXu12mig4NejLiUE5ILsGwnwGpN2PkNA+tqKoPiQ/+rTeBGRcvOTZ9TlcPvzoNb1olYEsA hk9m/fB59ygchU7ogk2ux5yZVTo1XSW7bCD2wvHoB6ETZxBe0aWQRMPXmnF/qq+iTrn0f8ApWCE L3Cjr0b7F+x41xastVbYHwAE= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta12.migadu.com with ESMTPS id eacc6b0cb29b5092; Fri, 02 Oct 2026 09:57:22 +0000 X-Mizu-Trace-ID: eacc6b0cb29b5092 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: [PATCH v8 24/30] mm/khugepaged: treat PMD swap entries as mapped THPs Date: Fri, 2 Oct 2026 02:52:38 -0700 Message-ID: <20261002095503.3585565-25-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261002095503.3585565-1-usama.arif@linux.dev> References: <20261002095503.3585565-1-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