From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E703C433FE for ; Sun, 6 Dec 2020 11:55:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8EA1E22C7D for ; Sun, 6 Dec 2020 11:55:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8EA1E22C7D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8AF646B005C; Sun, 6 Dec 2020 06:55:25 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8608F6B005D; Sun, 6 Dec 2020 06:55:25 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7506D6B0068; Sun, 6 Dec 2020 06:55:25 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0103.hostedemail.com [216.40.44.103]) by kanga.kvack.org (Postfix) with ESMTP id 5C8DD6B005C for ; Sun, 6 Dec 2020 06:55:25 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 0B989180AD807 for ; Sun, 6 Dec 2020 11:55:25 +0000 (UTC) X-FDA: 77562702210.20.shape71_5d08de8273d5 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id D88B6180C07AF for ; Sun, 6 Dec 2020 11:55:24 +0000 (UTC) X-HE-Tag: shape71_5d08de8273d5 X-Filterd-Recvd-Size: 2801 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Sun, 6 Dec 2020 11:55:24 +0000 (UTC) Date: Sun, 6 Dec 2020 13:55:17 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1607255723; bh=pTpsXS9CBriukmpy9E70AdN9gCV7E3J/symznTMEUrg=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=RXZ0B/nzOzWsaFVRvI6ZjRbJ6wLRT2dJpYT4Dt7VBca4QCoJuM5SAZWP1N9Pu/zwP L0kazA7TFH12wCnfSkkCxQTRejZRN8sxziNtu3cB7pIooUdr68wQNcKzu54/fLE5zu xnwwI8rDDYJtXoAFUd/xAh6zMjUP65QQ1iibZRGBVu0IejhJOk+5a9T5MYS+Iq2tq2 LvLFHCJWkIYU2MhLSN7IH7KJ8FC2fSJFiDiuhmU371o+pDxHUv8Z6uhPNWeqXyu2qR lXPXaJio9ZOXl85oNHrlnop5TKKk/ADvXD+jDklROb25kQ8o30K/7mtfnMe3MtzZKE ZrP/4TuXtqjxg== From: Mike Rapoport To: carver4lio@163.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hailong Liu Subject: Re: [PATCH] mm/memblock:use a more appropriate order calculation when free memblock pages Message-ID: <20201206115517.GL751215@kernel.org> References: <20201203152311.5272-1-carver4lio@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201203152311.5272-1-carver4lio@163.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Dec 03, 2020 at 11:23:10PM +0800, carver4lio@163.com wrote: > From: Hailong Liu > > When system in the booting stage, pages span from [start, end] of a memblock > are freed to buddy in a order as large as possible (less than MAX_ORDER) at > first, then decrease gradually to a proper order(less than end) in a loop. > > However, *min(MAX_ORDER - 1UL, __ffs(start))* can not get the largest order > in some cases. Do you have examples? What is the memory configration that casues suboptimal order selection and what is the order in this case? > Instead, *__ffs(end - start)* may be more appropriate and meaningful. As several people reported using __ffs(end - start) is not correct. If the order selection is indeed suboptimal we'd need some better formula ;-) > Signed-off-by: Hailong Liu > --- > mm/memblock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index b68ee8678..7c6d0dde7 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1931,7 +1931,7 @@ static void __init __free_pages_memory(unsigned long start, unsigned long end) > int order; > > while (start < end) { > - order = min(MAX_ORDER - 1UL, __ffs(start)); > + order = min(MAX_ORDER - 1UL, __ffs(end - start)); > > while (start + (1UL << order) > end) > order--; > -- > 2.17.1 > > -- Sincerely yours, Mike.