From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f178.google.com (mail-ob0-f178.google.com [209.85.214.178]) by kanga.kvack.org (Postfix) with ESMTP id 13EDD6B0032 for ; Thu, 15 Jan 2015 20:21:54 -0500 (EST) Received: by mail-ob0-f178.google.com with SMTP id gq1so16702356obb.9 for ; Thu, 15 Jan 2015 17:21:53 -0800 (PST) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id y4si897400obm.66.2015.01.15.17.21.52 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Thu, 15 Jan 2015 17:21:53 -0800 (PST) Message-ID: <54B867A8.6050900@oracle.com> Date: Thu, 15 Jan 2015 20:21:44 -0500 From: Sasha Levin MIME-Version: 1.0 Subject: Re: [Lsf-pc] [LSF/MM TOPIC] Reclaim in the face of really fast I/O References: <54B82A57.9060000@intel.com> In-Reply-To: <54B82A57.9060000@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen , Matthew Wilcox , lsf-pc@lists.linux-foundation.org, "Reddy, Dheeraj" Cc: "Kleen, Andi" , Linux-MM , "Chen, Tim C" On 01/15/2015 04:00 PM, Dave Hansen wrote: > I/O devices are only getting faster. In fact, they're getting closer > and closer to memory in latency and bandwidth. But the VM is still > designed to do very orderly and costly procedures to reclaim memory, and > the existing algorithms don't parallelize particularly well. They hit > contention on mmap_sem or the lru locks well before all of the CPU > horsepower that we have can be brought to bear on reclaim. > > Once the latency to bring pages in and out of storage becomes low > enough, reclaiming the _right_ pages becomes much less important than > doing something useful with the CPU horsepower that we have. > > We need to talk about ways to do reclaim with lower CPU overhead and to > parallelize more effectively. > > There has been some research in this area by some folks at Intel and we > could quickly summarize what has been learned so far to help kick off a > discussion. I was actually planning to bring that up. Trinity can cause enough stress to a system that the hang watchdog triggers (with a 10 minute timeout!) inside reclaim code. Thanks, Sasha -- 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