From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ea0-f174.google.com (mail-ea0-f174.google.com [209.85.215.174]) by kanga.kvack.org (Postfix) with ESMTP id C423E6B0039 for ; Fri, 10 Jan 2014 17:23:53 -0500 (EST) Received: by mail-ea0-f174.google.com with SMTP id b10so2300925eae.33 for ; Fri, 10 Jan 2014 14:23:53 -0800 (PST) Received: from jenni1.inet.fi (mta-out.inet.fi. [195.156.147.13]) by mx.google.com with ESMTP id p9si12474257eew.244.2014.01.10.14.23.53 for ; Fri, 10 Jan 2014 14:23:53 -0800 (PST) Date: Sat, 11 Jan 2014 00:23:15 +0200 From: "Kirill A. Shutemov" Subject: Re: [RFC PATCH] mm: thp: Add per-mm_struct flag to control THP Message-ID: <20140110222315.GA7931@node.dhcp.inet.fi> References: <1389383718-46031-1-git-send-email-athorlton@sgi.com> <20140110202310.GB1421@node.dhcp.inet.fi> <20140110220155.GD3066@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140110220155.GD3066@sgi.com> Sender: owner-linux-mm@kvack.org List-ID: To: Alex Thorlton , Mel Gorman , Andrea Arcangeli Cc: linux-mm@kvack.org, Ingo Molnar , Peter Zijlstra , Andrew Morton , "Kirill A. Shutemov" , Benjamin Herrenschmidt , Rik van Riel , Naoya Horiguchi , Oleg Nesterov , "Eric W. Biederman" , Andy Lutomirski , Al Viro , Kees Cook , linux-kernel@vger.kernel.org On Fri, Jan 10, 2014 at 04:01:55PM -0600, Alex Thorlton wrote: > On Fri, Jan 10, 2014 at 10:23:10PM +0200, Kirill A. Shutemov wrote: > > Do you know what cause the difference? I prefer to fix THP instead of > > adding new knob to disable it. > > The issue is that when you touch 1 byte of an untouched, contiguous 2MB > chunk, a THP will be handed out, and the THP will be stuck on whatever > node the chunk was originally referenced from. If many remote nodes > need to do work on that same chunk, they'll be making remote accesses. > With THP disabled, 4K pages can be handed out to separate nodes as > they're needed, greatly reducing the amount of remote accesses to > memory. I think this problem *potentially* could be fixed by NUMA balancer. (Although, I don't really know how balancer works...) If we see NUMA hint faults for addresses in different 4k pages inside huge page from more then one node, we could split the huge page. Mel, is it possible? Do we collect enough info to make the decision? -- Kirill A. Shutemov -- 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