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 B12CC1E493C for ; Tue, 6 May 2025 07:01:34 +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=1746514894; cv=none; b=gGdOa5f4eSR7YYa/3GmipUMJuoUpKtoi6JqqFOvZ1t+55FhKG2WUDPDmC7ANpAzJ9JtIOt0Ijm3heQcgpz9lQZenzlv+bdlvII2M1cTeiJPbHabh8qzS/GqkLYr6hzjzuwrn2bdYs7y+WxiDCvjXo9alnXhPpuD4JhOgt71SW4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746514894; c=relaxed/simple; bh=w9uxW/9oeSFU7jsO6s9mzRWQ4gOuUHQwYzTuGEWVL9o=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=ixkkGD7i8eY7WoJqsP1uYNcyLwDUFYhXeVL+SeN6QlTPh053enNSW7dJqFbOtNkBTf10OPca8YeQEKKGSs3dNTRwjD0FBVewoXWvD7924uy45BihRJJ5tjmyKD+oQwHZfmLiUCA+Lfn1sLyUKAPUVuAJrJQiBngkSau8rgYcLQ8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Z2sKxBHG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Z2sKxBHG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF136C4CEE4; Tue, 6 May 2025 07:01:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1746514894; bh=w9uxW/9oeSFU7jsO6s9mzRWQ4gOuUHQwYzTuGEWVL9o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Z2sKxBHGWSNf5nAr2gfqkZHaiqJbxdeG6vfjhfSsQ4BRL8KQ+qGKAPA5cV60+gjBF 3ih0N/yDF+NkQaMsBnlSt+2KOpIk8Lp8dRozkE+Q+xumyhpCsSffxzhzI1SXLlCw47 8+n+JFNfheL+OU2U7IWsvnAI9tMKShYL+aS6miZE= Date: Tue, 6 May 2025 00:01:33 -0700 From: Andrew Morton To: Juan Yescas Cc: Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, tjmercier@google.com, isaacmanjarres@google.com, surenb@google.com, kaleshsingh@google.com, Vlastimil Babka , "Liam R. Howlett" , Lorenzo Stoakes , David Hildenbrand , Mike Rapoport , Minchan Kim Subject: Re: [PATCH v3] mm: Add CONFIG_PAGE_BLOCK_ORDER to select page block order Message-Id: <20250506000133.ba44539dd517e4f54515751b@linux-foundation.org> In-Reply-To: <20250506002319.513795-1-jyescas@google.com> References: <20250506002319.513795-1-jyescas@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 5 May 2025 17:22:58 -0700 Juan Yescas wrote: > Problem: On large page size configurations (16KiB, 64KiB), the CMA > alignment requirement (CMA_MIN_ALIGNMENT_BYTES) increases considerably, > and this causes the CMA reservations to be larger than necessary. > This means that system will have less available MIGRATE_UNMOVABLE and > MIGRATE_RECLAIMABLE page blocks since MIGRATE_CMA can't fallback to them. > > The CMA_MIN_ALIGNMENT_BYTES increases because it depends on > MAX_PAGE_ORDER which depends on ARCH_FORCE_MAX_ORDER. The value of > ARCH_FORCE_MAX_ORDER increases on 16k and 64k kernels. > > ... > > +config PAGE_BLOCK_ORDER > + int "Page Block Order" > + range 1 10 if !ARCH_FORCE_MAX_ORDER > + default 10 if !ARCH_FORCE_MAX_ORDER > + range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER > + default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER Do we really need to do this arithmetic within Kconfig? Would it be cleaner to do this at runtime, presumably when calculating pageblock_order?