Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752119AbdLNNFR (ORCPT ); Thu, 14 Dec 2017 08:05:17 -0500 Received: from mx2.suse.de ([195.135.220.15]:37709 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751297AbdLNNFQ (ORCPT ); Thu, 14 Dec 2017 08:05:16 -0500 Date: Thu, 14 Dec 2017 14:04:35 +0100 From: Michal Hocko To: Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH V2] mm/mprotect: Add a cond_resched() inside change_pmd_range() Message-ID: <20171214130435.GL16951@dhcp22.suse.cz> References: <20171214111426.25912-1-khandual@linux.vnet.ibm.com> <20171214112928.GH16951@dhcp22.suse.cz> <28e54a80-73d9-76aa-31d5-f71375f14b96@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <28e54a80-73d9-76aa-31d5-f71375f14b96@linux.vnet.ibm.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2221 Lines: 60 On Thu 14-12-17 18:25:54, Anshuman Khandual wrote: > On 12/14/2017 04:59 PM, Michal Hocko wrote: > > On Thu 14-12-17 16:44:26, Anshuman Khandual wrote: > >> diff --git a/mm/mprotect.c b/mm/mprotect.c > >> index ec39f73..43c29fa 100644 > >> --- a/mm/mprotect.c > >> +++ b/mm/mprotect.c > >> @@ -196,6 +196,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > >> this_pages = change_pte_range(vma, pmd, addr, next, newprot, > >> dirty_accountable, prot_numa); > >> pages += this_pages; > >> + cond_resched(); > >> } while (pmd++, addr = next, addr != end); > >> > >> if (mni_start) > > > > this is not exactly what I meant. See how change_huge_pmd does continue. > > That's why I mentioned zap_pmd_range which does goto next... > > I might be still missing something but is this what you meant ? yes, except > Here we will give cond_resched() cover to the THP backed pages > as well. but there is still if (!is_swap_pmd(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) && pmd_none_or_clear_bad(pmd)) continue; so we won't have scheduling point on pmd holes. Maybe this doesn't matter, I haven't checked but why should we handle those differently? > diff --git a/mm/mprotect.c b/mm/mprotect.c > index ec39f73..3d445ee 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -188,7 +188,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > } > > /* huge pmd was handled */ > - continue; > + goto next; > } > } > /* fall through, the trans huge pmd just split */ > @@ -196,6 +196,8 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > this_pages = change_pte_range(vma, pmd, addr, next, newprot, > dirty_accountable, prot_numa); > pages += this_pages; > +next: > + cond_resched(); > } while (pmd++, addr = next, addr != end); > > if (mni_start) -- Michal Hocko SUSE Labs