From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 22 Nov 2000 16:11:04 +0200 From: Matti Aarnio Subject: Re: max memory limits ??? Message-ID: <20001122161104.C28963@mea-ext.zmailer.org> References: <3A1BCC05.4080608@SANgate.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3A1BCC05.4080608@SANgate.com>; from gabriel@SANgate.com on Wed, Nov 22, 2000 at 03:37:09PM +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: BenHanokh Gabriel Cc: linux-mm@kvack.org List-ID: On Wed, Nov 22, 2000 at 03:37:09PM +0200, BenHanokh Gabriel wrote: > hi > > can some1 explain the memory limits on the 2.4 kernel > > - what is the maximum amount of physical memory it supports ? There are some Alpha systems with 256 GB memory where Linux is sometimes tested. Those processors support up to several terabytes of memory (nobody built such maximum machines, though.) For intel machines limits are different, of course. (PAE36 supports up to 16*4 GB = 64 GB physical address space, within which there must be some holes to support e.g. PCI bus address spaces, and system boot rom, to name a few.) For intel ia64 -- that is a 64 bit machine, thus it propably follows Alpha and UltraSPARC model in this regard. > - what is the limit for user-space apps ? At 32 bit systems: 3.5 GB with extreme tricks, 3 GB for more usual. At 64 bit systems -- 2^60 or some such semi-meaningless value. > - what is the limit for kernel ? Whatever the hardware supports. > - are there any limits on malloc, static-memory, stack-memory ? userspace rules. > - does using HIGHMEM results with performance penalty ? Of course, it causes extra mapping operations on machines needing it to support larger memory (intel PAE36 featured hardware). User processes can access all what is mapped into them at the same time -- All programs, kernel included are limited to 32 bit addresses, but kernel can juggle maps to reach areas not mapped in its address space at some moment. > - anything else ? > > please CC me for any answer > > regards > Benhanokh Gabriel -- 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/