From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 17 May 2001 22:16:10 +0300 From: Matti Aarnio Subject: Re: Running out of vmalloc space Message-ID: <20010517221610.K5947@mea-ext.zmailer.org> References: <3B04069C.49787EC2@fc.hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3B04069C.49787EC2@fc.hp.com>; from dp@fc.hp.com on Thu, May 17, 2001 at 11:13:00AM -0600 Sender: owner-linux-mm@kvack.org Return-Path: To: David Pinedo Cc: linux-mm@kvack.org List-ID: On Thu, May 17, 2001 at 11:13:00AM -0600, David Pinedo wrote: [ Why vmalloc() space is so small ? ] Hua Ji summarized quite well what the kernel does, and where. There are 32bit machines which *can* access whole 4G kernel space separate from simultaneous 4G user space, however i386 is not one of those. PAE36 doesn't help either -- aside of the PHYSICAL memory addressability increase, the problem is in 4G choke point in address calculations which causes 32-bit segment register value be added on 32-bits address, but only for the low 32 bits, loosing "up-shifted" top 4 bits. The mapping tables will then expand that 32-bit result to 36 bits of PAE. If you can come up with some magic instruction which does data move from/to alternate memory mapping context than what is currently running (e.g. userspace or kernel), preferrably privileged instruction, a LOT of people would be very glad -- and very nearly overnight we could supply 4G space for both user and kernel spaces. In Motorola 68k series there is such a thing, called 'movec'. > Thanks for any information anyone can provide. > > David Pinedo > Hewlett-Packard Company > Fort Collins, Colorado > dp@fc.hp.com /Matti Aarnio -- who much prefers clean 64-bit pointers... -- 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.eu.org/Linux-MM/