Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 13 Dec 2001 05:28:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 13 Dec 2001 05:28:03 -0500 Received: from zikova.cvut.cz ([147.32.235.100]:37391 "EHLO zikova.cvut.cz") by vger.kernel.org with ESMTP id ; Thu, 13 Dec 2001 05:27:43 -0500 From: "Petr Vandrovec" Organization: CC CTU Prague To: Wayne Whitney Date: Thu, 13 Dec 2001 11:27:10 MET-1 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: Repost: could ia32 mmap() allocations grow downward? CC: LKML X-mailer: Pegasus Mail v3.40 Message-ID: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 12 Dec 01 at 22:28, Wayne Whitney wrote: > BTW, if one were trying to port some code that uses brk() directly and > even frees memory that way, then it seems that with glibc's malloc(), one > could make it work by instructing malloc() always to use mmap(). > P.S. I am 100% sure that the particular application of mine that started > me thinking about this, MAGMA, uses its own allocator built on top of > brk() and never calls malloc() itself. If you have legacy app, how it comes that it uses mmap? And if I do not use mmap, I have nothing at 1GB: void main() { sleep(10); brk((void*)0xBF000000); pause(); } /proc/`pidof x`/maps says during sleep(10): 08048000-080a1000 r-xp 00000000 03:03 230941 /usr/src/linus/x 080a1000-080a5000 rw-p 00058000 03:03 230941 /usr/src/linus/x 080a5000-080a6000 rwxp 00000000 00:00 0 bffff000-c0000000 rwxp 00000000 00:00 0 and after brk() (which suceeded after I did ulimit -d unlimited and 'echo 1 >/proc/sys/vm/overcommit_memory') I see: 08048000-080a1000 r-xp 00000000 03:03 230941 /usr/src/linus/x 080a1000-080a5000 rw-p 00058000 03:03 230941 /usr/src/linus/x 080a5000-bf000000 rwxp 00000000 00:00 0 bffff000-c0000000 rwxp 00000000 00:00 0 So maybe MAGMA uses some API which it should not use under any circumstances... Such as that you linked it with libc6 stdio. Best regards, Petr Vandrovec vandrove@vc.cvut.cz - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/