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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B35F1C43441 for ; Wed, 28 Nov 2018 23:36:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7228D21019 for ; Wed, 28 Nov 2018 23:36:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7228D21019 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726964AbeK2KjU (ORCPT ); Thu, 29 Nov 2018 05:39:20 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:40482 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726382AbeK2KjU (ORCPT ); Thu, 29 Nov 2018 05:39:20 -0500 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id E8EDAB4A; Wed, 28 Nov 2018 23:36:00 +0000 (UTC) Date: Wed, 28 Nov 2018 15:35:59 -0800 From: Andrew Morton To: Minchan Kim Cc: LKML , Sergey Senozhatsky , Joey Pabalinas Subject: Re: [PATCH v3 5/7] zram: support idle/huge page writeback Message-Id: <20181128153559.f6645b98a7033b6f6f6b0fbc@linux-foundation.org> In-Reply-To: <20181127055429.251614-6-minchan@kernel.org> References: <20181127055429.251614-1-minchan@kernel.org> <20181127055429.251614-6-minchan@kernel.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; 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 Tue, 27 Nov 2018 14:54:27 +0900 Minchan Kim wrote: > This patch supports new feature "zram idle/huge page writeback". > On zram-swap usecase, zram has usually many idle/huge swap pages. > It's pointless to keep in memory(ie, zram). > > To solve the problem, this feature introduces idle/huge page > writeback to backing device so the goal is to save more memory > space on embedded system. > > Normal sequence to use idle/huge page writeback feature is as follows, > > while (1) { > # mark allocated zram slot to idle > echo all > /sys/block/zram0/idle > # leave system working for several hours > # Unless there is no access for some blocks on zram, > # they are still IDLE marked pages. > > echo "idle" > /sys/block/zram0/writeback > or/and > echo "huge" > /sys/block/zram0/writeback > # write the IDLE or/and huge marked slot into backing device > # and free the memory. > } > > By per discussion: > https://lore.kernel.org/lkml/20181122065926.GG3441@jagdpanzerIV/T/#u, > > This patch removes direct incommpressibe page writeback feature > (d2afd25114f4, zram: write incompressible pages to backing device) > so we could regard it as regression because incompressible pages > doesn't go to backing storage automatically. Instead, usre should > do it via "echo huge" > /sys/block/zram/writeback" manually. I'm not in any position to determine the regression risk here. Why is that feature being removed, anyway? > If we hear some regression, we could restore the function. Why not do that now?