From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751513AbdBIL7O (ORCPT ); Thu, 9 Feb 2017 06:59:14 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50495 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750968AbdBIL7M (ORCPT ); Thu, 9 Feb 2017 06:59:12 -0500 Subject: Re: [PATCH 3/3] mm: Enable Buddy allocation isolation for CDM nodes To: Vlastimil Babka , 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: Anshuman Khandual Date: Thu, 9 Feb 2017 15:39:58 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17020910-0012-0000-0000-0000020F900E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17020910-0013-0000-0000-000006F65926 Message-Id: <81ae434a-0c67-c11a-e052-8b33b39c2152@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-02-09_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702090100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/2017 02:18 PM, Vlastimil Babka wrote: > 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? Hmm, think you are right. Then I can drop the last check there. Will test it out. Thanks for pointing this out.