FYI, see my reply on lkml too (it might start a thread of its own).

I recently had a quick look into why this is so when I heard some
other operating systems do better than us here.

I believe it is because we copy all page tables though we need not
copy those that are filebacked MAP_SHARED. The patch to change this
is fairly trivial, though I didn't have a real world test to justify
any improvement.

Actually, it may be worthwhile for another reason on large NUMA
systems so their leaf page tables get allocated on the same node
in which the memory is used.

Benjamin LaHaise wrote:

----- Forwarded message from Ray Fucillo [off-list ref] -----

Subject: process creation time increases linearly with shmem
From: Ray Fucillo <redacted>
To: linux-kernel@vger.kernel.org
Date: 	Wed, 24 Aug 2005 14:43:29 -0400
Resent-Message-Id: [off-list ref]
Resent-Sender: Benjamin LaHaise [off-list ref]
Resent-From: bcrl@kvack.org
Resent-Date: Wed, 24 Aug 2005 15:13:51 -0400
Resent-To: bcrl@linux.intel.com

I am seeing process creation time increase linearly with the size of the 
shared memory segment that the parent touches.  The attached forktest.c 
is a very simple user program that illustrates this behavior, which I 
have tested on various kernel versions from 2.4 through 2.6.  Is this a 
known issue, and is it solvable?

[snip]

-- 
SUSE Labs, Novell Inc.

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