From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 3B1F46B02C3 for ; Thu, 29 Jun 2017 02:14:59 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id g46so35135514wrd.3 for ; Wed, 28 Jun 2017 23:14:59 -0700 (PDT) Received: from mail-wm0-x233.google.com (mail-wm0-x233.google.com. [2a00:1450:400c:c09::233]) by mx.google.com with ESMTPS id s17si3261937wra.76.2017.06.28.23.14.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Jun 2017 23:14:58 -0700 (PDT) Received: by mail-wm0-x233.google.com with SMTP id b184so2830596wme.1 for ; Wed, 28 Jun 2017 23:14:57 -0700 (PDT) Subject: Re: [Bug 196157] New: 100+ times slower disk writes on 4.x+/i386/16+RAM, compared to 3.x References: <20170622123736.1d80f1318eac41cd661b7757@linux-foundation.org> <20170623071324.GD5308@dhcp22.suse.cz> <3541d6c3-6c41-8210-ee94-fef313ecd83d@gmail.com> <20170623113837.GM5308@dhcp22.suse.cz> <20170626054623.GC31972@dhcp22.suse.cz> <7b78db49-e0d8-9ace-bada-a48c9392a8ca@gmail.com> <20170626091254.GG11534@dhcp22.suse.cz> From: Alkis Georgopoulos Message-ID: <5eff5b8f-51ab-9749-0da5-88c270f0df92@gmail.com> Date: Thu, 29 Jun 2017 09:14:55 +0300 MIME-Version: 1.0 In-Reply-To: <20170626091254.GG11534@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , linux-mm@kvack.org, bugzilla-daemon@bugzilla.kernel.org, Mel Gorman , Johannes Weiner I've been working on a system with highmem_is_dirtyable=1 for a couple of hours. While the disk benchmark showed no performance hit on intense disk activity, there are other serious problems that make this workaround unusable. I.e. when there's intense disk activity, the mouse cursor moves with extreme lag, like 1-2 fps. Switching with alt+tab from e.g. thunderbird to pidgin needs 10 seconds. kswapd hits 100% cpu usage. Etc etc, the system becomes unusable until the disk activity settles down. I was testing via SSH so I hadn't noticed the extreme lag. All those symptoms go away when resetting highmem_is_dirtyable=0. So currently 32bit installations with 16 GB RAM have no option but to remove the extra RAM... About ab8fabd46f81 ("mm: exclude reserved pages from dirtyable memory"), would it make sense for me to compile a kernel and test if everything works fine without it? I.e. if we see that this caused all those regressions, would it be revisited? And an unrelated idea, is there any way to tell linux to use a limited amount of RAM for page cache, e.g. only 1 GB? Kind regards, Alkis Georgopoulos -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org