From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752084AbeBAPyo (ORCPT ); Thu, 1 Feb 2018 10:54:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34184 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751508AbeBAPyn (ORCPT ); Thu, 1 Feb 2018 10:54:43 -0500 Subject: Re: [RFC PATCH v1 00/13] lru_lock scalability To: daniel.m.jordan@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: aaron.lu@intel.com, ak@linux.intel.com, akpm@linux-foundation.org, Dave.Dice@oracle.com, dave@stgolabs.net, khandual@linux.vnet.ibm.com, ldufour@linux.vnet.ibm.com, mgorman@suse.de, mhocko@kernel.org, pasha.tatashin@oracle.com, steven.sistare@oracle.com, yossi.lev@oracle.com References: <20180131230413.27653-1-daniel.m.jordan@oracle.com> From: Steven Whitehouse Message-ID: <6bd1c8a5-c682-a3ce-1f9f-f1f53b4117a9@redhat.com> Date: Thu, 1 Feb 2018 15:54:38 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180131230413.27653-1-daniel.m.jordan@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 31/01/18 23:04, daniel.m.jordan@oracle.com wrote: > lru_lock, a per-node* spinlock that protects an LRU list, is one of the > hottest locks in the kernel. On some workloads on large machines, it > shows up at the top of lock_stat. > > One way to improve lru_lock scalability is to introduce an array of locks, > with each lock protecting certain batches of LRU pages. > > *ooooooooooo**ooooooooooo**ooooooooooo**oooo ... > | || || || > \ batch 1 / \ batch 2 / \ batch 3 / > > In this ASCII depiction of an LRU, a page is represented with either '*' > or 'o'. An asterisk indicates a sentinel page, which is a page at the > edge of a batch. An 'o' indicates a non-sentinel page. > > To remove a non-sentinel LRU page, only one lock from the array is > required. This allows multiple threads to remove pages from different > batches simultaneously. A sentinel page requires lru_lock in addition to > a lock from the array. > > Full performance numbers appear in the last patch in this series, but this > prototype allows a microbenchmark to do up to 28% more page faults per > second with 16 or more concurrent processes. > > This work was developed in collaboration with Steve Sistare. > > Note: This is an early prototype. I'm submitting it now to support my > request to attend LSF/MM, as well as get early feedback on the idea. Any > comments appreciated. > > > * lru_lock is actually per-memcg, but without memcg's in the picture it > becomes per-node. GFS2 has an lru list for glocks, which can be contended under certain workloads. Work is still ongoing to figure out exactly why, but this looks like it might be a good approach to that issue too. The main purpose of GFS2's lru list is to allow shrinking of the glocks under memory pressure via the gfs2_scan_glock_lru() function, and it looks like this type of approach could be used there to improve the scalability, Steve. > > Aaron Lu (1): > mm: add a percpu_pagelist_batch sysctl interface > > Daniel Jordan (12): > mm: allow compaction to be disabled > mm: add lock array to pgdat and batch fields to struct page > mm: introduce struct lru_list_head in lruvec to hold per-LRU batch > info > mm: add batching logic to add/delete/move API's > mm: add lru_[un]lock_all APIs > mm: convert to-be-refactored lru_lock callsites to lock-all API > mm: temporarily convert lru_lock callsites to lock-all API > mm: introduce add-only version of pagevec_lru_move_fn > mm: add LRU batch lock API's > mm: use lru_batch locking in release_pages > mm: split up release_pages into non-sentinel and sentinel passes > mm: splice local lists onto the front of the LRU > > include/linux/mm_inline.h | 209 +++++++++++++++++++++++++++++++++++++++++++++- > include/linux/mm_types.h | 5 ++ > include/linux/mmzone.h | 25 +++++- > kernel/sysctl.c | 9 ++ > mm/Kconfig | 1 - > mm/huge_memory.c | 6 +- > mm/memcontrol.c | 5 +- > mm/mlock.c | 11 +-- > mm/mmzone.c | 7 +- > mm/page_alloc.c | 43 +++++++++- > mm/page_idle.c | 4 +- > mm/swap.c | 208 ++++++++++++++++++++++++++++++++++++--------- > mm/vmscan.c | 49 +++++------ > 13 files changed, 500 insertions(+), 82 deletions(-) >