Re: TASK_UNMAPPED_BASE & stack location

From: William Lee Irwin III <wli@holomorphy.com>
To: Rik van Riel <riel@redhat.com>
Cc: "Martin J. Bligh" <mbligh@aracnet.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mm mailing list <linux-mm@kvack.org>,
	Andrew Morton <akpm@digeo.com>
Subject: Re: TASK_UNMAPPED_BASE & stack location
Date: Sat, 26 Apr 2003 08:03:45 -0700	[thread overview]
Message-ID: <20030426150345.GV8978@holomorphy.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0304261034180.27719-100000@chimarrao.boston.redhat.com>

On Fri, 25 Apr 2003, Martin J. Bligh wrote:
>> Is there any good reason we can't remove TASK_UNMAPPED_BASE, and just shove
>> libraries directly above the program text? Red Hat seems to have patches to
>> dynamically tune it on a per-processes basis anyway ...

On Sat, Apr 26, 2003 at 10:37:11AM -0400, Rik van Riel wrote:
> What could be done is leave the stack where it is, but have
> malloc() space and mmap() space grow towards each other:
> 0                                            3G
> | |prog | malloc -->         <-- mmap | stack |
> The stack will get the stack size ulimit size and the space
> between where malloc and mmap start should be about 2.7 GB.
> That 2.7 GB will of course by divided between malloc and mmap,
> but the division will be done dynamically based on whoever
> needs the space.  Much better than the current static 1:1.7
> division...

My internal proposals (backed by code) already include this in addition
to relocating the stack (whose kernel side is trivial).

-- wli