From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 5740728089F for ; Thu, 9 Feb 2017 03:48:22 -0500 (EST) Received: by mail-wr0-f197.google.com with SMTP id 89so7615119wrr.1 for ; Thu, 09 Feb 2017 00:48:22 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q4si916938wma.39.2017.02.09.00.48.20 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 09 Feb 2017 00:48:20 -0800 (PST) Subject: Re: [PATCH 3/3] mm: Enable Buddy allocation isolation for CDM nodes 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> From: Vlastimil Babka Message-ID: Date: Thu, 9 Feb 2017 09:48:18 +0100 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: owner-linux-mm@kvack.org List-ID: To: Anshuman Khandual , linux-kernel@vger.kernel.org, linux-mm@kvack.org 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 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? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org