From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752435AbdBNKRF (ORCPT ); Tue, 14 Feb 2017 05:17:05 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:50590 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751921AbdBNKPt (ORCPT ); Tue, 14 Feb 2017 05:15:49 -0500 Subject: Re: [PATCH V2 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: <20170210100640.26927-1-khandual@linux.vnet.ibm.com> <20170210100640.26927-4-khandual@linux.vnet.ibm.com> <44bbca4e-af5a-805c-c74b-28e684026611@suse.cz> 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: Tue, 14 Feb 2017 15:44:40 +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: <44bbca4e-af5a-805c-c74b-28e684026611@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17021410-0048-0000-0000-000002055454 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17021410-0049-0000-0000-000047878941 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-02-14_05:,, 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-1702140104 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/14/2017 01:58 PM, Vlastimil Babka wrote: > On 02/10/2017 11:06 AM, 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 | 16 ++++++++++++++++ >> 1 file changed, 16 insertions(+) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 84d61bb..392c24a 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -64,6 +64,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -2908,6 +2909,21 @@ 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; >> + } >> + } > > With the current cpuset implementation, this will have a subtle corner > case when allocating from a cpuset that allows the cdm node, and there > is no (task or vma) mempolicy applied for the allocation. In the fast > path (__alloc_pages_nodemask()) we'll set ac->nodemask to > current->mems_allowed, so your code will wrongly assume that this > ac->nodemask is a policy that allows the CDM node. Probably not what you > want? You are right, its a problem and not what we want. We can make the function get_page_from_freelist() take another parameter "orig_nodemask" which gets passed into __alloc_pages_nodemask() in the first place. So inside zonelist iterator we can compare orig_nodemask with current ac.nodemask to figure out if cpuset swapping of nodemask happened and skip CDM node if necessary. Thats a viable solution IMHO. > > This might change if we decide to fix the cpuset vs mempolicy issues [1] > so your input on that topic with your recent experience with all the > alternative CDM isolation implementations would be useful. Thanks. > > [1] http://www.spinics.net/lists/linux-mm/msg121760.html Sure, will look into the details.