From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx143.postini.com [74.125.245.143]) by kanga.kvack.org (Postfix) with SMTP id 102216B0101 for ; Fri, 5 Apr 2013 11:02:50 -0400 (EDT) Received: by mail-qa0-f44.google.com with SMTP id o13so336076qaj.10 for ; Fri, 05 Apr 2013 08:02:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <515CF884.8010103@gmail.com> References: <20130325134247.GB1393@localhost.localdomain> <515CF884.8010103@gmail.com> From: Andrew Shewmaker Date: Fri, 5 Apr 2013 09:02:29 -0600 Message-ID: Subject: Re: [PATCH v7 2/2] mm: replace hardcoded 3% with admin_reserve_pages knob Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Simon Jeons Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, alan@lxorguk.ukuu.org.uk, ric.masonn@gmail.com On Wed, Apr 3, 2013 at 9:50 PM, Simon Jeons wrote: >> FAQ >> ... >> * How do you calculate a minimum useful reserve? >> >> A user or the admin needs enough memory to login and perform >> recovery operations, which includes, at a minimum: >> >> sshd or login + bash (or some other shell) + top (or ps, kill, etc.) >> >> For overcommit 'guess', we can sum resident set sizes (RSS). >> On x86_64 this is about 8MB. >> >> For overcommit 'never', we can take the max of their virtual sizes >> (VSZ) >> and add the sum of their RSS. >> On x86_64 this is about 128MB. > > > 1.Why has this different between guess and never? The default, overcommit 'guess' mode, only needs a reserve for what the recovery programs will typically use. Overcommit 'never' mode will only successfully launch an app when it can fulfill all of its requested memory allocations--even if the app only uses a fraction of what it asks for. > 2.You just test x86/x86_64, other platforms also will use memory overcommit, > did you test them? No, I haven't. Unfortunately, I don't currently have any other platforms to test with. I'll see what I can do. Thanks, Andrew -- 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