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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 E154FC433DF for ; Wed, 1 Jul 2020 02:48:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0300206EB for ; Wed, 1 Jul 2020 02:48:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593571681; bh=WTGi74V/M6JRB3BLDWs0zeSTaQWxQakpQtHy05f1GGg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=q/+yNYIlpehMqVwCNSE8jLJ6mWExXHpZGLb8fNw222+8RovLIGj7dX7MnEc59b7DT m+n8JJze4JHj1olhCETuImsEfBA9RRN/UAwrvp/knHFEXEeIz59I+PS96mhQrqM3lu 4HbPhDxOZj4+EXhkAUDF6yWkUlReMFXalvSyNu7U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726919AbgGACsA (ORCPT ); Tue, 30 Jun 2020 22:48:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:40846 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbgGACr7 (ORCPT ); Tue, 30 Jun 2020 22:47:59 -0400 Received: from X1 (071-093-078-081.res.spectrum.com [71.93.78.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C8C58206EB; Wed, 1 Jul 2020 02:47:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593571678; bh=WTGi74V/M6JRB3BLDWs0zeSTaQWxQakpQtHy05f1GGg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mUY4V98q0IugIwaSjIBz0UE5DT7Y59IxduswVw5uo7NzpDfjNo8GRdV8kvAjjGnyO x5HTMhgZAaqfXE8borCroalaROYxeqO2w/SSgJvvqfiCG5M1TyV0+fKDmIKsNVfi/Z arubItYYt+8QyyeRmClKXcCdrjIOYglPFyJuWc70= Date: Tue, 30 Jun 2020 19:47:55 -0700 From: Andrew Morton To: Dave Hansen Cc: Baoquan He , Dave Hansen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, ben.widawsky@intel.com, alex.shi@linux.alibaba.com, dwagner@suse.de, tobin@kernel.org, cl@linux.com, stable@kernel.org Subject: Re: [PATCH] mm/vmscan: restore zone_reclaim_mode ABI Message-Id: <20200630194755.61f56a55d46222f8d0c84bdd@linux-foundation.org> In-Reply-To: <791c47ad-5a6b-1f1b-c34b-d8bbf7722957@intel.com> References: <20200626003459.D8E015CA@viggo.jf.intel.com> <20200629065203.GJ3346@MiWiFi-R3L-srv> <3ba94f19-3b18-9d52-a070-f652620c88e6@intel.com> <20200629233043.GK3346@MiWiFi-R3L-srv> <791c47ad-5a6b-1f1b-c34b-d8bbf7722957@intel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 29 Jun 2020 16:37:37 -0700 Dave Hansen wrote: > On 6/29/20 4:30 PM, Baoquan He wrote: > >> The only way I can plausibly think of "cleaning up" the RECLAIM_ZONE bit > >> would be to raise our confidence that it is truly unused. That takes > >> time, and probably a warning if we see it being set. If we don't run > >> into anybody setting it or depending on it being set in a few years, we > >> can remove it. > > So adding the old bit back for compatibility looks good, thanks. > > > > Then we have to be very careful when adding and reviewing new > > interface introducing, should not leave one which might be used > > in the future. > > > > In fact, RECLAIM_ZONE is not completely useless. At least, when the old > > bit 0 is set, it may enter into node_reclaim() in get_page_from_freelist(), > > that makes it like a switch. > > > > get_page_from_freelist { > > > > ... > > if (node_reclaim_mode == 0 || > > !zone_allows_reclaim(ac->preferred_zoneref->zone, zone)) > > continue; > > ... > > } > > Oh, that's a very good point. There are a couple of those around. Let > me circle back and update the documentation and the variable name. I'll > send out another version. Was the omission of cc:stable deliberate?