From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753368AbbATFxi (ORCPT ); Tue, 20 Jan 2015 00:53:38 -0500 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:55873 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750722AbbATFxe (ORCPT ); Tue, 20 Jan 2015 00:53:34 -0500 From: "Aneesh Kumar K.V" To: Vlastimil Babka , Andrew Morton Cc: "Kirill A. Shutemov" , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V3] mm/thp: Allocate transparent hugepages on local node In-Reply-To: <54BD308A.4080905@suse.cz> References: <1421393196-20915-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20150116160204.544e2bcf9627f5a4043ebf8d@linux-foundation.org> <54BD308A.4080905@suse.cz> User-Agent: Notmuch/0.19+2~g32855b9 (http://notmuchmail.org) Emacs/25.0.50.1 (x86_64-pc-linux-gnu) Date: Tue, 20 Jan 2015 11:22:58 +0530 Message-ID: <87fvb6uhfp.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15012005-0009-0000-0000-000000D2517F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vlastimil Babka writes: > On 01/17/2015 01:02 AM, Andrew Morton wrote: >> On Fri, 16 Jan 2015 12:56:36 +0530 "Aneesh Kumar K.V" wrote: >> >>> This make sure that we try to allocate hugepages from local node if >>> allowed by mempolicy. If we can't, we fallback to small page allocation >>> based on mempolicy. This is based on the observation that allocating pages >>> on local node is more beneficial than allocating hugepages on remote node. >> >> The changelog is a bit incomplete. It doesn't describe the current >> behaviour, nor what is wrong with it. What are the before-and-after >> effects of this change? >> >> And what might be the user-visible effects? >> >>> --- a/mm/mempolicy.c >>> +++ b/mm/mempolicy.c >>> @@ -2030,6 +2030,46 @@ retry_cpuset: >>> return page; >>> } >>> >>> +struct page *alloc_hugepage_vma(gfp_t gfp, struct vm_area_struct *vma, >>> + unsigned long addr, int order) >> >> alloc_pages_vma() is nicely documented. alloc_hugepage_vma() is not >> documented at all. This makes it a bit had for readers to work out the >> difference! >> >> Is it possible to scrunch them both into the same function? Probably >> too messy? > > Hm that could work, alloc_pages_vma already has an if (MPOL_INTERLEAVE) part, so > just put the THP specialities into an "else if (huge_page)" part there? > > You could probably test for GFP_TRANSHUGE the same way as __alloc_pages_slowpath > does. There might be false positives theoretically, but is there anything else > that would use these flags and not be a THP? > is that check correct ? ie, if ((gfp & GFP_TRANSHUGE) == GFP_TRANSHUGE) may not always indicate transparent hugepage if defrag = 0 . With defrag cleared, we remove __GFP_WAIT from GFP_TRANSHUGE. static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) { return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; } -aneesh