From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx185.postini.com [74.125.245.185]) by kanga.kvack.org (Postfix) with SMTP id 92ABB6B0032 for ; Wed, 21 Aug 2013 12:23:16 -0400 (EDT) Message-ID: <5214E96B.3090009@intel.com> Date: Wed, 21 Aug 2013 09:23:07 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH 2/2] mm: add overcommit_kbytes sysctl variable References: <1376925478-15506-1-git-send-email-jmarchan@redhat.com> <1376925478-15506-2-git-send-email-jmarchan@redhat.com> <52124DE7.8070502@intel.com> <5214DB1B.6070803@redhat.com> In-Reply-To: <5214DB1B.6070803@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Marchand Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 08/21/2013 08:22 AM, Jerome Marchand wrote: >> > Instead of introducing yet another tunable, why don't we just make the >> > ratio that comes in from the user more fine-grained? >> > >> > sysctl overcommit_ratio=0.2 >> > >> > We change the internal 'sysctl_overcommit_ratio' to store tenths or >> > hundreths of a percent (or whatever), then parse the input as two >> > integers. I don't think we need fully correct floating point parsing >> > and rounding here, so it shouldn't be too much of a chore. It'd >> > probably end up being less code than you have as it stands. >> > > Now that I think about it, that could break user space. Sure write access > wouldn't be a problem (one can still write a plain integer), but a script > that reads a fractional value when it expects an integer might not be able > to cope with it. You're right. Something doing FOO=$(cat overcommit_ratio) and then trying do do arithmetic would just fail loudly. But, it would probably fail silently if we create another tunable that all of a sudden returns 0 (when the kernel is not _behaving_ like it is set to 0). I'm not sure there's a good way out of this without breakage (or at least confusing) of _some_ old scripts/programs. Either way has ups and downs. The existing dirty_ratio/bytes stuff just annoys me because I end up having to check two places whenever I go looking for it. -- 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