From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 6822F6B0044 for ; Tue, 27 Oct 2009 14:18:32 -0400 (EDT) Subject: Re: RFC: Transparent Hugepage support From: Andi Kleen References: <20091026185130.GC4868@random.random> Date: Tue, 27 Oct 2009 19:18:26 +0100 In-Reply-To: <20091026185130.GC4868@random.random> (Andrea Arcangeli's message of "Mon, 26 Oct 2009 19:51:30 +0100") Message-ID: <87ljiwk8el.fsf@basil.nowhere.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Izik Eidus , Hugh Dickins , Nick Piggin , Andrew Morton List-ID: Andrea Arcangeli writes: In general the best would be to just merge hugetlbfs into the normal VM. It has been growing for far too long as a separate "second VM" by now. This seems like a reasonable first step, but some comments blow. Haven't looked at the actual code at this point. > Second important decision (to reduce the impact of the feature on the > existing pagetable handling code) is that at any time we can split an > hugepage into 512 regular pages and it has to be done with an > operation that can't fail. This way the reliability of the swapping > isn't decreased (no need to allocate memory when we are short on > memory to swap) and it's trivial to plug a split_huge_page* one-liner > where needed without polluting the VM. Over time we can teach The problem is that this will interact badly with 1GB pages -- once you split them up you'll never get them back, because they can't be allocated at runtime. Even for 2MB pages it can be a problem. You'll likely need to fix the page table code. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org