Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753959AbdCOPow (ORCPT ); Wed, 15 Mar 2017 11:44:52 -0400 Received: from mga07.intel.com ([134.134.136.100]:38154 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753144AbdCOPoA (ORCPT ); Wed, 15 Mar 2017 11:44:00 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,169,1486454400"; d="scan'208";a="1142636734" Date: Wed, 15 Mar 2017 23:44:07 +0800 From: Aaron Lu To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen , Tim Chen , Andrew Morton , Ying Huang Subject: Re: [PATCH v2 0/5] mm: support parallel free of memory Message-ID: <20170315154406.GF2442@aaronlu.sh.intel.com> References: <1489568404-7817-1-git-send-email-aaron.lu@intel.com> <20170315141813.GB32626@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170315141813.GB32626@dhcp22.suse.cz> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1335 Lines: 28 On Wed, Mar 15, 2017 at 03:18:14PM +0100, Michal Hocko wrote: > On Wed 15-03-17 16:59:59, Aaron Lu wrote: > [...] > > The proposed parallel free did this: if the process has many pages to be > > freed, accumulate them in these struct mmu_gather_batch(es) one after > > another till 256K pages are accumulated. Then take this singly linked > > list starting from tlb->local.next off struct mmu_gather *tlb and free > > them in a worker thread. The main thread can return to continue zap > > other pages(after freeing pages pointed by tlb->local.pages). > > I didn't have a look at the implementation yet but there are two > concerns that raise up from this description. Firstly how are we going > to tune the number of workers. I assume there will be some upper bound > (one of the patch subject mentions debugfs for tuning) and secondly The workers are put in a dedicated workqueue which is introduced in patch 3/5 and the number of workers can be tuned through that workqueue's sysfs interface: max_active. > if we offload the page freeing to the worker then the original context > can consume much more cpu cycles than it was configured via cpu > controller. How are we going to handle that? Or is this considered > acceptable? I'll need to think about and take a look at this subject(not familiar with cpu controller). Thanks.