From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756138Ab3I3P2U (ORCPT ); Mon, 30 Sep 2013 11:28:20 -0400 Received: from www.sr71.net ([198.145.64.142]:36741 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755347Ab3I3P2S (ORCPT ); Mon, 30 Sep 2013 11:28:18 -0400 Message-ID: <52499875.4060101@sr71.net> Date: Mon, 30 Sep 2013 08:27:49 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Mel Gorman , Andrew Morton CC: "Kirill A. Shutemov" , Andrea Arcangeli , Al Viro , Hugh Dickins , Wu Fengguang , Jan Kara , linux-mm@kvack.org, Andi Kleen , Matthew Wilcox , "Kirill A. Shutemov" , Hillf Danton , Ning Qu , Alexander Shishkin , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv6 00/22] Transparent huge page cache: phase 1, everything but mmap() References: <1379937950-8411-1-git-send-email-kirill.shutemov@linux.intel.com> <20130924163740.4bc7db61e3e520798220dc4c@linux-foundation.org> <20130930100249.GB2425@suse.de> In-Reply-To: <20130930100249.GB2425@suse.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/30/2013 03:02 AM, Mel Gorman wrote: > I am afraid I never looked too closely once I learned that the primary > motivation for this was relieving iTLB pressure in a very specific > case. AFAIK, this is not a problem in the vast majority of modern CPUs > and I found it very hard to be motivated to review the series as a result. > I suspected that in many cases that the cost of IO would continue to dominate > performance instead of TLB pressure. I also found it unlikely that there > was a workload that was tmpfs based that used enough memory to be hurt > by TLB pressure. My feedback was that a much more compelling case for the > series was needed but this discussion all happened on IRC unfortunately. FWIW, I'm mostly intrigued by the possibilities of how this can speed up _software_, and I'm rather uninterested in what it can do for the TLB. Page cache is particularly painful today, precisely because hugetlbfs and anonymous-thp aren't available there. If you have an app with hundreds of GB of files that it wants to mmap(), even if it's in the page cache, it takes _minutes_ to just fault in. One example: https://lkml.org/lkml/2013/6/27/698