From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752011AbdBIIs0 (ORCPT ); Thu, 9 Feb 2017 03:48:26 -0500 Received: from mx2.suse.de ([195.135.220.15]:46936 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751777AbdBIIsY (ORCPT ); Thu, 9 Feb 2017 03:48:24 -0500 Subject: Re: [PATCH 3/3] mm: Enable Buddy allocation isolation for CDM nodes To: Anshuman Khandual , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20170208140148.16049-1-khandual@linux.vnet.ibm.com> <20170208140148.16049-4-khandual@linux.vnet.ibm.com> <8ef1de25-d4fd-482c-c55e-df93d0730484@suse.cz> <8982ccfc-3b96-89bd-60e6-471971aee609@linux.vnet.ibm.com> Cc: mhocko@suse.com, mgorman@suse.de, minchan@kernel.org, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, srikar@linux.vnet.ibm.com, haren@linux.vnet.ibm.com, jglisse@redhat.com, dave.hansen@intel.com, dan.j.williams@intel.com From: Vlastimil Babka Message-ID: Date: Thu, 9 Feb 2017 09:48:18 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <8982ccfc-3b96-89bd-60e6-471971aee609@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/2017 06:05 AM, Anshuman Khandual wrote: > On 02/08/2017 10:48 PM, Vlastimil Babka wrote: >> On 02/08/2017 03:01 PM, Anshuman Khandual wrote: >>> This implements allocation isolation for CDM nodes in buddy allocator by >>> discarding CDM memory zones all the time except in the cases where the >>> gfp >>> flag has got __GFP_THISNODE or the nodemask contains CDM nodes in cases >>> where it is non NULL (explicit allocation request in the kernel or user >>> process MPOL_BIND policy based requests). >>> >>> Signed-off-by: Anshuman Khandual >>> --- >>> mm/page_alloc.c | 19 +++++++++++++++++++ >>> 1 file changed, 19 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 40908de..7d8c82a 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -64,6 +64,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include >>> #include >>> @@ -2908,6 +2909,24 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned >>> int order, int alloc_flags, >>> struct page *page; >>> unsigned long mark; >>> >>> + /* >>> + * CDM nodes get skipped if the requested gfp flag >>> + * does not have __GFP_THISNODE set or the nodemask >>> + * does not have any CDM nodes in case the nodemask >>> + * is non NULL (explicit allocation requests from >>> + * kernel or user process MPOL_BIND policy which has >>> + * CDM nodes). >>> + */ >>> + if (is_cdm_node(zone->zone_pgdat->node_id)) { >>> + if (!(gfp_mask & __GFP_THISNODE)) { >>> + if (!ac->nodemask) >>> + continue; >>> + >>> + if (!nodemask_has_cdm(*ac->nodemask)) >>> + continue; >> >> nodemask_has_cdm() looks quite expensive, combined with the loop here >> that's O(n^2). But I don't understand why you need it. If there is no >> cdm node in the nodemask, then we never reach this code with a cdm node, >> because the zonelist iterator already checks the nodemask? Am I missing >> something? > > A CDM zone can be selected during zonelist iteration if > > (1) If nodemask is NULL (where all zones are eligible) > > (1) Skip it if __GFP_THISNODE is not mentioned > (2) Pick it if __GFP_THISNODE is mentioned > > (2) If nodemask has CDM (where CDM zones are eligible) > > (1) Pick it if nodemask has CDM > (2) Pick it if __GFP_THISNODE is mentioned > > (1) (1) Enforces the primary isolation > (2) (1) Is the only option which could be O(n^2) as the worst case > > Checking for both the zone being a CDM zone and the nodemask containing > CDM node has to happen together for (2) (1). But we dont run into this > option unless we have first checked if request contains __GFP_THISNODE > and that nodemask is really a non NULL value. Hence the number cases > getting into (2) (1) should be less. IIUC only the user space MPOL_BIND > ones will come here. Maybe I'm still missing something, but when you do nodemask_has_cdm() above then we already passed "if (!ac->nodemask) continue" which means ac->nodemask is not null, which means the zonelist iterator already did the filtering on ac->nodemask, and if this zone passed the filter and it's a cdm zone, then it has to be set in the nodemask?