From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xJGjC1761zDrK6 for ; Fri, 28 Jul 2017 01:53:18 +1000 (AEST) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6RFrCDK035507 for ; Thu, 27 Jul 2017 11:53:16 -0400 Received: from e36.co.us.ibm.com (e36.co.us.ibm.com [32.97.110.154]) by mx0a-001b2d01.pphosted.com with ESMTP id 2byjw2gt8n-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 27 Jul 2017 11:53:14 -0400 Received: from localhost by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 27 Jul 2017 09:53:02 -0600 Subject: Re: [RFC PATCH 2/3] powerpc/mm: Implement pmdp_establish for ppc64 To: Michal Hocko Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, "Kirill A . Shutemov" , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org References: <20170727083756.32217-1-aneesh.kumar@linux.vnet.ibm.com> <20170727083756.32217-2-aneesh.kumar@linux.vnet.ibm.com> <20170727125644.GC27766@dhcp22.suse.cz> From: "Aneesh Kumar K.V" Date: Thu, 27 Jul 2017 21:22:55 +0530 MIME-Version: 1.0 In-Reply-To: <20170727125644.GC27766@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: <1cd105a8-5d07-0768-867c-54e678f5f828@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 07/27/2017 06:26 PM, Michal Hocko wrote: > On Thu 27-07-17 14:07:55, Aneesh Kumar K.V wrote: >> We can now use this to set pmd page table entries to absolute values. THP >> need to ensure that we always update pmd PTE entries such that we never mark >> the pmd none. pmdp_establish helps in implementing that. >> >> This doesn't flush the tlb. Based on the old_pmd value returned caller can >> decide to call flush_pmd_tlb_range() > > _Why_ do we need this. It doesn't really help that the newly added > function is not used so we could check that... We were looking at having pmdp_establish used by the core code. But i guess Kirill ended up using pmdp_invalidate. If we don't have pmdp_establish usage in core code, we can drop this. This is to help Kiril make progress with series at https://lkml.kernel.org/r/20170615145224.66200-1-kirill.shutemov@linux.intel.com Also thinking about the interface further, I guess pmdp_establish interface is some what confusing. So we may want to rethink this further. I know that i asked for pmdp_establish in earlier review of Kirill's patchset. But now looking back i am not sure we can clearly explain only semantic requirement of pmdp_establish. One thing we may want to clarify is whether we should retain the Reference and change bit from the old entry when we are doing a pmdp_establish ? Kirill, Considering core code is still only using pmdp_invalidate(), we may want to drop this interface completely ? -aneesh