From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 20F016B0260 for ; Mon, 5 Dec 2016 04:25:40 -0500 (EST) Received: by mail-wm0-f71.google.com with SMTP id i131so15902402wmf.3 for ; Mon, 05 Dec 2016 01:25:40 -0800 (PST) Received: from mail-wj0-f177.google.com (mail-wj0-f177.google.com. [209.85.210.177]) by mx.google.com with ESMTPS id t10si7003767wmb.0.2016.12.05.01.25.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 05 Dec 2016 01:25:38 -0800 (PST) Received: by mail-wj0-f177.google.com with SMTP id tg4so28873174wjb.1 for ; Mon, 05 Dec 2016 01:25:38 -0800 (PST) Date: Mon, 5 Dec 2016 10:25:37 +0100 From: Michal Hocko Subject: Re: Silly question about dethrottling Message-ID: <20161205092536.GE30758@dhcp22.suse.cz> References: <20161205070519.GA30765@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Raymond Jennings Cc: Linux Memory Management List On Mon 05-12-16 01:15:39, Raymond Jennings wrote: > On Sun, Dec 4, 2016 at 11:05 PM, Michal Hocko wrote: > > > On Sun 04-12-16 13:56:54, Raymond Jennings wrote: > > > I have an application that is generating HUGE amounts of dirty data. > > > Multiple GiB worth, and I'd like to allow it to fill at least half of my > > > RAM. > > > > Could you be more specific why and what kind of problem you are trying > > to solve? > > > > > I already have /proc/sys/vm/dirty_ratio pegged at 80 and the background > > one > > > pegged at 50. RAM is 32GiB. > > > > There is also dirty_bytes alternative which is an absolute numer. > > > > How does this compare to setting dirty_ratio to a high percentage? Well, dirty_bytes is an absolute number when to start to throttle while ratio is relative to node_dirtyable_memory > > > it appears to be butting heads with clean memory. How do I tell my > > system > > > to prefer using RAM to soak up writes instead of caching? > > > > I am not sure I understand. Could you be more specific about what is the > > actual problem? Is it possible that your dirty data is already being > > flushed and that is wy you see a clean cache? > > > > What I'm wanting is for my writing process not to get throttled, even when > the dirty memory it starts creating starts hogging memory the system would > rather use for cache. Then you can configure dirty_background_{bytes,ratio} to start flushing dirty data sooner. Having a lot of dirty data in the system just asks for troubles elsewhere as it would take a lot of time to sync that to the backing store. That means that many unrelated processes might get stuck on sync etc. for an unconfortably large amount of time. -- Michal Hocko SUSE Labs -- 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