From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Date: Wed, 26 Mar 2008 23:21:43 +0000 Subject: Re: larger default page sizes... Message-Id: <20080326.162143.244048620.davem@davemloft.net> List-Id: References: <87wsnrgg9q.fsf@basil.nowhere.org> <18409.56843.909298.717089@cargo.ozlabs.ibm.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: clameter@sgi.com Cc: paulus@samba.org, andi@firstfloor.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, torvalds@linux-foundation.org From: Christoph Lameter 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.