From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8B10735C1A3 for ; Tue, 6 Jan 2026 18:46:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767725192; cv=none; b=XIp3g6qRbKfs6QSgapfnYU6Fu6CzKn1qHTW1fcdBXr/DYvf4Bxz0x6D9avYGhkXT5Bud/KMcusM+KfToo5XzuioqrPpjRYxghpP3u3ASK9K+EiG9+GOYLQ7bJZm1tQEkpa6avDREg8CESLaOjjBQfIebdt9ZEpYpmRKHJFNVxt8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767725192; c=relaxed/simple; bh=KpOiVaXPjG1PAae7sFpgxWI7yXFuwOVZaMip5iXibeo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mvqZ6OZQWYrj6KaQzOXRl2L8UlVyYVVmpTdUe+GV4Lj1WFU4sXi6oWZK4qweJk7AyGHsRiEAaJGQ6yvy6+nxymSbZGeZ8DcGUzyiDBwvMz5VyDc6ypIW3zyFy30TCCGbI2HKjo7o26F5DPCvFZG9kmVKDW7+un+ZQxgANQe1Y/U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OzV1Iic2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OzV1Iic2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93274C19423; Tue, 6 Jan 2026 18:46:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767725191; bh=KpOiVaXPjG1PAae7sFpgxWI7yXFuwOVZaMip5iXibeo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=OzV1Iic2K0TUMTrBbT5fK8X7C6A4aWz4pzAe1tPMBnx2TNo1FW33ZkD7Z9ZhYEHYX udfnJ64qUWrQJoRZAdTf2ftf16YShoGKjSjv3CaTjsdCeN4mz8ziGZW/yIdOsv7kjB UFIm/no8sqYVSrF+wVlV0cgar5KDdyFdUARp+cKOlyLRt3zPJnKHBxp7k3nt5GTYsc AK2wUk4OhuJJk99B+3K2oFhMNQBlyXQCOsH8LDFQvZXpYXW9Z1yY8LjKUMcNzAb+Z3 iX6u6RGXIVCQz9xKP4RSZBVgjiOHYu9710GYkZiqa5QPIaxp69RIZdIfBX3ZG/UgnD Cwj1Yo3RS+uTA== Message-ID: <9c807ff8-b4ad-43d5-8034-ec7fcd0fe5d6@kernel.org> Date: Tue, 6 Jan 2026 19:46:25 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7] page_alloc: allow migration of smaller hugepages during contig_alloc To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, richard.weiyang@gmail.com References: <20251221124656.2362540-1-gourry@gourry.net> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit > - return false; > + /* > + * Only consider ranges containing hugepages if those pages are > + * smaller than the requested contiguous region. e.g.: > + * Move 2MB pages to free up a 1GB range. > + * Don't move 1GB pages to free up a 2MB range. > + * > + * This makes contiguous allocation more reliable if multiple > + * hugepage sizes are used without causing needless movement. > + */ > + if (PageHuge(page)) { > + unsigned int order; > + > + if (!IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION)) > + return false; > + > + if (skip_hugetlb) { > + *skipped_hugetlb = true; > + return false; > + } > + > + page = compound_head(page); > + order = compound_order(page); > + if ((order >= MAX_FOLIO_ORDER) || > + (nr_pages <= (1 << order))) > + return false; > + > + /* > + * Reaching this point means we've encounted a huge page > + * smaller than nr_pages, skip all pfn's for that page. > + * > + * We can't get here from a tail-PageHuge, as it implies > + * we started a scan in the middle of a hugepage larger > + * than nr_pages - which the prior check filters for. > + */ > + i += (1 << order) - 1; Assuming page != compound_head(page), you'd be skipping too much. You'd only have to skip as many pages as pages are left in this compound page. I think we have similar code elsewhere: see has_unmovable_pages(). Apart from that LGTM. -- Cheers David