From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www23.ureach.com (IDENT:root@www23.ureach.com [172.16.2.51]) by ureach.com (8.9.1/8.8.5) with ESMTP id HAA23909 for ; Fri, 6 Jul 2001 07:14:51 -0400 Date: Fri, 6 Jul 2001 07:14:51 -0400 Message-Id: <200107061114.HAA13294@www23.ureach.com> From: Kapish K Reply-to: Subject: vmalloc limits Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org List-ID: Hello, we were looking at some code to understand the vmalloc limits under different memory ranges and the capacity to change them and their implications. Here's our understanding and we would like to know the implications of some changes as well... MAXMEM actually specifies the maximum physical RAM that is addressible in the kernel virtual memory. So, under the current i386 code of an intel 32 bit machine, with a VMALLOC_RESERVE value of 128mb, it implies that this MAXMEM is around 896mb ( 1024mb - 128mb ). So, our understanding is this: on systems with physical ram less than this MAXMEM capacity, the end of physical ram mapped kernel virtual address space marks the beginning of vmalloc area, i.e., VMALLOC_START. However, in the limiting case of ram equalling the MAXMEM value, the VMALLOC_RESERVE value determines the start of vmalloc area, which implies that on such systems with ram >= say 896 mb, VMALLOC_RESERVE decides how much area is available for vmalloc. I suppose this understanding is right. If not please point the place where I may be going wrong. Now, if we were to increase the VMALLOC_RESERVE to a higher value of say 256 mb or so, that would mean increasing the vmalloc area. But what other subtle implications might this have? of course, another option as someone already suggested on this list ( there was an earlier discussion on vmalloc on this list ) about changing the page_offset value and thereby increasing the size, but we would be interested in the higher memory cases, where the limiting VMALLOC_RESERVE would determine the vmalloc area. Any pointers or hints to known issues with this kind of change will be welcome. We can follow it up from thereon. Thanks in Advance ________________________________________________ Get your own "800" number Voicemail, fax, email, and a lot more http://www.ureach.com/reg/tag -- 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/