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Date: Tue, 4 Dec 2001 14:42:28 -0200 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
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To: Peter Zaitsev <pz@spylog.ru>
Cc: Andrea Arcangeli <andrea@suse.de>, Andrew Morton <akpm@zip.com.au>,
        <theowl@freemail.c3.hu>, <theowl@freemail.hu>,
        <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@transmeta.com>
Subject: Re[2]: your mail on mmap() to the kernel list
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On Tue, 4 Dec 2001, Peter Zaitsev wrote:
> Tuesday, December 04, 2001, 5:15:49 PM, you wrote:

> AA> You can fix the problem in userspace by using a meaningful 'addr' as
> AA> hint to mmap(2), or by using MAP_FIXED from userspace, then the kernel
> AA> won't waste time searching the first available mapping over
> AA> TASK_UNMAPPED_BASE.

> Well. Really you can't do this, because you can not really track all of
> the mappings in user program as glibc and probably other libraries
> use mmap for their purposes.

There's no reason we couldn't do this hint in kernel space.

In arch_get_unmapped_area we can simply keep track of the
lowest address where we found free space, while on munmap()
we can adjust this hint if needed.

OTOH, I doubt it would help real-world workloads where the
application maps and unmaps areas of different sizes and
actually does something with the memory instead of just
mapping and unmapping it ;)))

kind regards,

Rik
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