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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 5A74FC433E0 for ; Wed, 24 Jun 2020 11:13:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1C0182082F for ; Wed, 24 Jun 2020 11:13:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="uu6sySxg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C0182082F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8C5496B0002; Wed, 24 Jun 2020 07:13:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 878D86B0003; Wed, 24 Jun 2020 07:13:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 764AD6B0005; Wed, 24 Jun 2020 07:13:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0076.hostedemail.com [216.40.44.76]) by kanga.kvack.org (Postfix) with ESMTP id 5D4E96B0002 for ; Wed, 24 Jun 2020 07:13:21 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DE88C180AD807 for ; Wed, 24 Jun 2020 11:13:20 +0000 (UTC) X-FDA: 76963844160.18.rings77_59166b926e43 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id B6DF1100EDBEB for ; Wed, 24 Jun 2020 11:13:20 +0000 (UTC) X-HE-Tag: rings77_59166b926e43 X-Filterd-Recvd-Size: 3036 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Wed, 24 Jun 2020 11:13:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=o+wrDuDEOBRD8xp7VlW4WFiVlPd+yRCvyexu2cGK4ug=; b=uu6sySxgKDDgJoBHjuKpYnDFAk wN1sRUtDSglgsjM9dH3HJQY2ht+gocnxs5fhwqVMQGAoSxpqRg7RLJfv2nRzPCS5Ff1FpO2FUuSd/ qov/JJCwkeBAD7uR7wzz1IbVsZmg8OxSIxpckpafKijTLjzwEUcWEBWvngmfL07YqIld10vXxeKDk 6nD46lnLCecuY/LMaH71FiMAMXwyzTcH9hMLhGEieuw/q5Zh6InPKVuJRW42p8ia/ICsyIvnm91PN pVWKARuUQTm7I6AxHamRvcbmrh+/UmrgLMcViXKSXocoAHlLbNqwhJ2niGopF1lz6ye4+hQSt3Urw bRg5UoDQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo3Kp-0008Jh-8M; Wed, 24 Jun 2020 11:12:55 +0000 Date: Wed, 24 Jun 2020 12:12:55 +0100 From: Matthew Wilcox To: Joel Savitz Cc: linux-kernel@vger.kernel.org, Vlastimil Babka , John Hubbard , Andrew Morton , Rafael Aquini , linux-mm@kvack.org Subject: Re: [PATCH] mm/page_alloc: fix documentation error and remove magic numbers Message-ID: <20200624111255.GL21350@casper.infradead.org> References: <20200624032712.23263-1-jsavitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624032712.23263-1-jsavitz@redhat.com> X-Rspamd-Queue-Id: B6DF1100EDBEB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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 Tue, Jun 23, 2020 at 11:27:12PM -0400, Joel Savitz wrote: > In addition, this patch replaces the magic number bounds with symbolic > constants to clarify the logic. Why do people think this kind of thing makes the code easier to read? It actually makes it harder. Unless the constants are used in more than one place, just leave the numbers where they are. > @@ -7852,6 +7852,9 @@ void setup_per_zone_wmarks(void) > * 8192MB: 11584k > * 16384MB: 16384k > */ > +static const int MIN_FREE_KBYTES_LOWER_BOUND = 1 << 7; > +static const int MIN_FREE_KBYTES_UPPER_BOUND = 1 << 18; > + > int __meminit init_per_zone_wmark_min(void) > { > unsigned long lowmem_kbytes; > @@ -7862,10 +7865,10 @@ int __meminit init_per_zone_wmark_min(void) > > if (new_min_free_kbytes > user_min_free_kbytes) { > min_free_kbytes = new_min_free_kbytes; > - if (min_free_kbytes < 128) > - min_free_kbytes = 128; > - if (min_free_kbytes > 262144) > - min_free_kbytes = 262144; > + if (min_free_kbytes < MIN_FREE_KBYTES_LOWER_BOUND) > + min_free_kbytes = MIN_FREE_KBYTES_LOWER_BOUND; > + if (min_free_kbytes > MIN_FREE_KBYTES_UPPER_BOUND) > + min_free_kbytes = MIN_FREE_KBYTES_UPPER_BOUND; The only thing I'd consider changing there is replacing 262144 with 256 * 1024. 1 << 18 is not clearer!