From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932336AbdJZODh (ORCPT ); Thu, 26 Oct 2017 10:03:37 -0400 Received: from mga03.intel.com ([134.134.136.65]:42159 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932234AbdJZODd (ORCPT ); Thu, 26 Oct 2017 10:03:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,434,1503385200"; d="scan'208";a="914033678" Subject: Re: [PATCH v4] Add /proc/PID/smaps support for DAX To: Fan Du , akpm@linux-foundation.org, hch@lst.de, dan.j.williams@intel.com, mhocko@kernel.org References: <5A90DA2E42F8AE43BC4A093BF06788481AA50489@SHSMSX104.ccr.corp.intel.com> <1508994790-15427-1-git-send-email-fan.du@intel.com> Cc: linux-kernel@vger.kernel.org From: Dave Hansen Message-ID: <482dcf1c-6013-c800-3e95-7476b9e52020@intel.com> Date: Thu, 26 Oct 2017 07:03:01 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1508994790-15427-1-git-send-email-fan.du@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I'm honestly not understanding what problem this solves. Could you, perhaps, do a before and after of smaps with and without this patch? > +/* page structure behind DAX mappings is NOT compound page > + * when it's a huge page mappings, so introduce new API to > + * account for both PMD and PUD mapping. > + */ Why do they need to be compound? Why don't we just make them compound instead of adding all this code which is *just* for DAX? > +static void smaps_account_dax_huge(struct mem_size_stats *mss, > + struct page *page, unsigned long size, bool young, bool dirty) > +{ > + int mapcount = page_mapcount(page); > + > + if (PageAnon(page)) { > + mss->anonymous += size; > + if (!PageSwapBacked(page) && !dirty && !PageDirty(page)) > + mss->lazyfree += size; > + } How can you have DAX anonymous huge pages? > + mss->resident += size; > + /* Accumulate the size in pages that have been accessed. */ > + if (young || page_is_young(page) || PageReferenced(page)) > + mss->referenced += size; Isn't this just a copy'n'paste of smaps_account() code? > + /* > + * page_count(page) == 1 guarantees the page is mapped exactly once. > + * If any subpage of the compound page mapped with PTE it would elevate > + * page_count(). > + */ > + if (page_count(page) == 1) { > + if (dirty || PageDirty(page)) > + mss->private_dirty += size; > + else > + mss->private_clean += size; > + mss->pss += (u64)size << PSS_SHIFT; > + return; > + } PSS makes *zero* sense for DAX. The "memory" is used whether the mapping exists or not. Also, the idea of "private" doesn't really make sense here. > + if (mapcount >= 2) { > + if (dirty || PageDirty(page)) > + mss->shared_dirty += size; > + else > + mss->shared_clean += size; > + mss->pss += (size << PSS_SHIFT) / mapcount; > + } else { > + if (dirty || PageDirty(page)) > + mss->private_dirty += size; > + else > + mss->private_clean += size; > + mss->pss += size << PSS_SHIFT; > + } > +} > + > #ifdef CONFIG_SHMEM > static int smaps_pte_hole(unsigned long addr, unsigned long end, > struct mm_walk *walk) > @@ -528,7 +577,16 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr, > struct page *page = NULL; > > if (pte_present(*pte)) { > - page = vm_normal_page(vma, addr, *pte); > + if (!vma_is_dax(vma)) > + page = vm_normal_page(vma, addr, *pte); > + else if (pte_devmap(*pte)) { > + struct dev_pagemap *pgmap; > + > + pgmap = get_dev_pagemap(pte_pfn(*pte), NULL); > + if (!pgmap) > + return; > + page = pte_page(*pte); > + } > } else if (is_swap_pte(*pte)) { > swp_entry_t swpent = pte_to_swp_entry(*pte); > > @@ -579,7 +637,19 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr, > struct page *page; > > /* FOLL_DUMP will return -EFAULT on huge zero page */ > - page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); > + if (!vma_is_dax(vma)) > + page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); > + else if (pmd_devmap(*pmd)) { > + struct dev_pagemap *pgmap; > + > + pgmap = get_dev_pagemap(pmd_pfn(*pmd), NULL); > + if (!pgmap) > + return; > + page = pmd_page(*pmd); > + smaps_account_dax_huge(mss, page, PMD_SIZE, pmd_young(*pmd), > + pmd_dirty(*pmd)); > + return; > + } > if (IS_ERR_OR_NULL(page)) > return; > if (PageAnon(page)) > There's a fair amount of copying and pasting going on here. There is, again, a bunch of specialized DAX code. Isn't there a way to do this more generically?