From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: [-mm PATCH] Memory controller improve user interface Date: Thu, 30 Aug 2007 03:57:07 +0530 Message-ID: <46D5F2BB.8010203@linux.vnet.ibm.com> References: <20070829111030.9987.8104.sendpatchset@balbir-laptop> <1188413148.28903.113.camel@localhost> <46D5ED5C.9030405@linux.vnet.ibm.com> <1188425894.28903.140.camel@localhost> Reply-To: balbir@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1188425894.28903.140.camel@localhost> Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen Cc: Andrew Morton , Linux Kernel Mailing List , Linux MM Mailing List , David Rientjes , Linux Containers , Paul Menage List-Id: containers.vger.kernel.org Dave Hansen wrote: > On Thu, 2007-08-30 at 03:34 +0530, Balbir Singh wrote: >> I've thought about this before. The problem is that a user could >> set his limit to 10000 bytes, but would then see the usage and >> limit round to the closest page boundary. This can be confusing >> to a user. > > True, but we're lying if we allow a user to set their limit there, > because we can't actually enforce a limit at 8,192 bytes vs 10,000. > They're the same limit as far as the kernel is concerned. > > Why not just -EINVAL if the value isn't page-aligned? There are plenty > of interfaces in the kernel that require userspace to know the page > size, so this shouldn't be too difficult. True, mmap() is a good example of such an interface for developers, I am not sure about system admins though. To quote Andrew Reporting tools could run getpagesize() and do the arithmetic, but we generally try to avoid exposing PAGE_SIZE, HZ, etc to userspace in this manner. -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL