linux-kernel - Re: larger default page sizes...

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Message-Id: <20080326.162143.244048620.davem@davemloft.net>
Date:	Wed, 26 Mar 2008 16:21:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	clameter@....com
Cc:	paulus@...ba.org, andi@...stfloor.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: Re: larger default page sizes...

From: Christoph Lameter <clameter@....com>
Date: Wed, 26 Mar 2008 10:56:17 -0700 (PDT)

> One should emphasize that this test was a kernel compile which is not 
> a load that gains much from larger pages.

Actually, ever since gcc went to a garbage collecting allocator, I've
found it to be a TLB thrasher.

It will repeatedly randomly walk over a GC pool of at least 8MB in
size, which to fit fully in the TLB with 4K pages reaquires a TLB with
2048 entries assuming gcc touches no other data which is of course a
false assumption.

For some compiles this GC pool is more than 100MB in size.

GCC does not fit into any modern TLB using it's base page size.
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