From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4D6DF287247 for ; Wed, 10 Jun 2026 11:34:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781091254; cv=none; b=ONbyngbWn66AyB4dfLJSyZ91ZLqm6cdt79a1Yyi2Ji0PdGba0wvFVUdqFs0vHnjG1Dotq4cy1h0awSiwWW0VRPlGboruOQ7FZ4K4eFbGg9dheRkuo89C7wFaRfAD08Ek6uKCPdLE58gJuo8v4DHbc3X1iK4v9Mu0Ro7aA0JCgdc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781091254; c=relaxed/simple; bh=Q1lB1yIPnHpdXh4d+KiI+259dRqDSyD3N8GF7VwoK1o=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=Ks3WsquTRn90fkyr73zSI+i4FFZOD9x/8bZ+g1AVmyziq2eR2Pbs5/oBb5F1lro3+95BPr03vZpwOmwh9qN7+O1Rc94kIZoqP2hnFklCF7zBvNc5B6IjMGRM1YKIeARtUXWUZ42mx89/piN3JGEWdAQycrhHtPsKVesm1j6V/2c= 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=nMgRuPUs; arc=none smtp.client-ip=91.218.175.180 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="nMgRuPUs" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781091241; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XkPIYc6BxTC1Yyureze7Jc2IGyRH65P2wbDPNEliW2Q=; b=nMgRuPUsEF8gQiESTcWPWxWWBTGfXbuGadgVqAI4pbIRJufF1wFEEr2lZqs/7Nyb2C0vL+ A9avhuVNiCQ1fylOgqDEFHvbXwWvJoZD5BykXWoB21ypEEzJ1tcQT7AW/yw6ZfIZ4mC2fW /hr0stp5on41u8nUGq09svg8KurEuaE= From: Lance Yang To: baolin.wang@linux.alibaba.com Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, hughd@google.com, willy@infradead.org, ziy@nvidia.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 06/11] mm: khugepaged: allow khugepaged to check all shmem mTHP-sized orders Date: Wed, 10 Jun 2026 19:33:52 +0800 Message-Id: <20260610113352.25352-1-lance.yang@linux.dev> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On Wed, Jun 10, 2026 at 06:29:14PM +0800, Baolin Wang wrote: >We are now ready to enable shmem mTHP collapse, allowing >thp_vma_allowable_orders() to check all permissible shmem large orders. > >Signed-off-by: Baolin Wang >--- > mm/khugepaged.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > >diff --git a/mm/khugepaged.c b/mm/khugepaged.c >index 75b18ec4a6c3..a87918b7e18c 100644 >--- a/mm/khugepaged.c >+++ b/mm/khugepaged.c >@@ -578,9 +578,14 @@ static unsigned long collapse_possible_orders(struct vm_area_struct *vma, > { > unsigned long orders; > >- /* If khugepaged is scanning an anonymous vma, allow mTHP collapse */ >+ /* >+ * If khugepaged is scanning an anonymous or shmem vma, >+ * allow mTHP collapse. >+ */ > if ((tva_flags == TVA_KHUGEPAGED) && vma_is_anonymous(vma)) > orders = THP_ORDERS_ALL_ANON; >+ else if ((tva_flags == TVA_KHUGEPAGED) && vma_is_shmem(vma)) >+ orders = THP_ORDERS_ALL_FILE_DEFAULT; Hmm... for shmem, is the lower bound in mthp_collapse() expected? #define KHUGEPAGED_MIN_MTHP_ORDER 2 #define THP_ORDERS_ALL_FILE_DEFAULT \ ((BIT(MAX_PAGECACHE_ORDER + 1) - 1) & ~BIT(0)) KHUGEPAGED_MIN_MTHP_ORDER is 2, which was introduced for anon collapse. For shmem, though, we're feeding mthp_collapse() orders from THP_ORDERS_ALL_FILE_DEFAULT, and that only filter out order-0 ... if (order > KHUGEPAGED_MIN_MTHP_ORDER && (enabled_orders & GENMASK(order - 1, 0))) { order--; continue; } So order-1 never gets a chance. The walker stops at order-2 and never tries it, right? > else > orders = BIT(HPAGE_PMD_ORDER); > >-- >2.47.3 > >