From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e1.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m9ANIohc015549 for ; Fri, 10 Oct 2008 19:18:50 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m9ANIoOT258616 for ; Fri, 10 Oct 2008 19:18:50 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m9ANIniL013713 for ; Fri, 10 Oct 2008 19:18:50 -0400 Date: Fri, 10 Oct 2008 16:18:44 -0700 From: Gary Hade Subject: Re: [PATCH 1/2] [REPOST] mm: show node to memory section relationship with symlinks in sysfs Message-ID: <20081010231844.GA1718@us.ibm.com> References: <20081009192115.GB8793@us.ibm.com> <20081010124239.f92b5568.akpm@linux-foundation.org> <20081010213357.GD7369@us.ibm.com> <20081010145950.f51def29.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081010145950.f51def29.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Gary Hade , linux-mm@kvack.org, linux-kernel@vger.kernel.org, y-goto@jp.fujitsu.com, pbadari@us.ibm.com, mel@csn.ul.ie, lcm@us.ibm.com, mingo@elte.hu, greg@kroah.com, dave@linux.vnet.ibm.com, nish.aravamudan@gmail.com List-ID: On Fri, Oct 10, 2008 at 02:59:50PM -0700, Andrew Morton wrote: > On Fri, 10 Oct 2008 14:33:57 -0700 > Gary Hade wrote: > > > On Fri, Oct 10, 2008 at 12:42:39PM -0700, Andrew Morton wrote: > > > On Thu, 9 Oct 2008 12:21:15 -0700 > > > Gary Hade wrote: > > > > > > > Show node to memory section relationship with symlinks in sysfs > > > > > > > > Add /sys/devices/system/node/nodeX/memoryY symlinks for all > > > > the memory sections located on nodeX. For example: > > > > /sys/devices/system/node/node1/memory135 -> ../../memory/memory135 > > > > indicates that memory section 135 resides on node1. > > > > > > I'm not seeing here a description of why the kernel needs this feature. > > > Why is it useful? How will it be used? What value does it have to > > > our users? > > > > Sorry, I should have included that. In our case, it is another > > small step towards eventual total node removal. We will need to > > know which memory sections to offline for whatever node is targeted > > for removal. However, I suspect that exposing the node to section > > information to user-level could be useful for other purposes. > > For example, I have been thinking that using memory hotremove > > functionality to modify the amount of available memory on specific > > nodes without having to physically add/remove DIMMs might be useful > > to those that test application or benchmark performance on a > > multi-node system in various memory configurations. > > > > hm, OK, thanks. It does sound a bit thin, and if we merge this then > not only do we get a porkier kernel, Would you feel the same about the size increase if patch 2/2 (include memory section subtree in sysfs with only sparsemem enabled) was withdrawn? Without patch 2/2 the size increase for non-Sparsemem or Sparsemem wo/memory hotplug kernels is extremely small. Even for memory hotplug enabled kernels there is only a little extra code in ./drivers/base/node.o which only gets linked into NUMA enabled kernels. I can gather some numbers if necessary. > we also get a new userspace interface which we're then locked into. True. > > So I'm inclined to skip this change until we have a stronger need? Of course, I'm not. :) Gary -- Gary Hade System x Enablement IBM Linux Technology Center 503-578-4503 IBM T/L: 775-4503 garyhade@us.ibm.com http://www.ibm.com/linux/ltc -- 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