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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1726056116; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=N2Px+gv3Ilo41s2lPNRNvpyvLmyMLfN878LEASwZ+NA=; b=CDxS8pnnA+T6/S6dwvYSRxHQJkf5td8gqBZk1jB8b8otSHxWDcs0SJpBxiGIo1LSJ900lo MAkOhJ2QLlZVA/SYhIwSsbsHW0smLqPeHfB+7aY6nEWrqhe12CMjnJBvzYLR5seDF1ZRyr vBqgVkY5znYEPYiFZVteRkz9xwdaUG4= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 00D431007; Wed, 11 Sep 2024 05:02:53 -0700 (PDT) Received: from [10.162.40.31] (e116581.arm.com [10.162.40.31]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E1C7F3F66E; Wed, 11 Sep 2024 05:02:14 -0700 (PDT) Message-ID: <5d910327-fbf0-46ed-9655-846236b555db@arm.com> Date: Wed, 11 Sep 2024 17:32:11 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] mm: Abstract THP allocation To: David Hildenbrand , akpm@linux-foundation.org, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, mark.rutland@arm.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, jglisse@google.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240911065600.1002644-1-dev.jain@arm.com> <20240911065600.1002644-2-dev.jain@arm.com> <6eb09b5b-b23b-4bae-9629-b86df3570e06@redhat.com> Content-Language: en-US From: Dev Jain In-Reply-To: <6eb09b5b-b23b-4bae-9629-b86df3570e06@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 63A00180010 X-Rspamd-Server: rspam01 X-Stat-Signature: 9a3wqzefw9jqxox4ww377sgkt4gu76ay X-HE-Tag: 1726056144-150749 X-HE-Meta: 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 jrg+HqPM oWTQF9rqvL6NM6jRWJIYHEoL756C7QwpegUJH3YbURtn0ttmnUr/uh26QO9823Ik6L71LZjJhTwEyBsktc4sGpRsLyzn4uaHmydzhto2IgDbn2wlOrakCcKTuK7yptTNWfnDeKP1/fr/mSA5ptsCHIbGFiPlSSmJ339nB/9ibB8Bu3WkdWgPuYouH0RL2CXeswpBfck9JMirWzzK9BPqDC7nViouugBYMFEQdollIOgOJa44= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/11/24 14:59, David Hildenbrand wrote: > On 11.09.24 11:27, David Hildenbrand wrote: >> On 11.09.24 08:55, Dev Jain wrote: >>> In preparation for the second patch, abstract away the THP allocation >>> logic present in the create_huge_pmd() path, which corresponds to the >>> faulting case when no page is present. >>> >>> There should be no functional change as a result of applying >>> this patch. >>> >> >> Hi, >> >>> Signed-off-by: Dev Jain >>> --- >>>    mm/huge_memory.c | 110 >>> +++++++++++++++++++++++++++++------------------ >>>    1 file changed, 67 insertions(+), 43 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 67c86a5d64a6..b96a1ff2bf40 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -943,47 +943,88 @@ unsigned long thp_get_unmapped_area(struct >>> file *filp, unsigned long addr, >>>    } >>>    EXPORT_SYMBOL_GPL(thp_get_unmapped_area); >>>    -static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault >>> *vmf, >>> -            struct page *page, gfp_t gfp) >>> +static struct folio *pmd_thp_fault_alloc(gfp_t gfp, struct >>> vm_area_struct *vma, >>> +                     unsigned long haddr, unsigned long addr) >> >> I suggest calling this something like "vma_alloc_anon_folio_pmd()"? Then >> it's more consistent with vma_alloc_folio(). >> >> Also, likely we should just only pass in "addr" and calculate "haddr" >> ourselves, it's cheap and reduces the number of function parameters. >> >>>    { >>> -    struct vm_area_struct *vma = vmf->vma; >>> -    struct folio *folio = page_folio(page); >>> -    pgtable_t pgtable; >>> -    unsigned long haddr = vmf->address & HPAGE_PMD_MASK; >>> -    vm_fault_t ret = 0; >>> +    const int order = HPAGE_PMD_ORDER; >>> +    struct folio *folio = vma_alloc_folio(gfp, order, vma, haddr, >>> true); >>>    -    VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); >>> +    if (unlikely(!folio)) { >>> +        count_vm_event(THP_FAULT_FALLBACK); >>> +        count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK); >>> +        goto out; >>> +    } >>>    +    VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); >>>        if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) { >>>            folio_put(folio); >>>            count_vm_event(THP_FAULT_FALLBACK); >>>            count_vm_event(THP_FAULT_FALLBACK_CHARGE); >>> -        count_mthp_stat(HPAGE_PMD_ORDER, >>> MTHP_STAT_ANON_FAULT_FALLBACK); >>> -        count_mthp_stat(HPAGE_PMD_ORDER, >>> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); >>> -        return VM_FAULT_FALLBACK; >>> +        count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK); >>> +        count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); >>> +        goto out; >>>        } >>>        folio_throttle_swaprate(folio, gfp); >>>    -    pgtable = pte_alloc_one(vma->vm_mm); >>> -    if (unlikely(!pgtable)) { >>> -        ret = VM_FAULT_OOM; >>> -        goto release; >>> -    } >>> - >>> -    folio_zero_user(folio, vmf->address); >>> +    folio_zero_user(folio, addr); >>>        /* >>>         * The memory barrier inside __folio_mark_uptodate makes sure >>> that >>>         * folio_zero_user writes become visible before the set_pmd_at() >>>         * write. >>>         */ >>>        __folio_mark_uptodate(folio); >>> +out: >>> +    return folio; >>> +} >>> + >>> +static void __pmd_thp_fault_success_stats(struct vm_area_struct *vma) >>> +{ >>> +    count_vm_event(THP_FAULT_ALLOC); >>> +    count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC); >>> +    count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC); >>> +} >> >> Why isn't that moved into map_pmd_thp() >> >> Note that in this patch you do: >> >> map_pmd_thp(folio, vmf, vma, haddr); >> spin_unlock(vmf->ptl); >> __pmd_thp_fault_success_stats(vma); >> >> But in patch #2 >> >> map_pmd_thp(folio, vmf, vma, haddr); >> __pmd_thp_fault_success_stats(vma); >> goto unlock; >> release: >>     folio_put(folio); >> unlock: >>     spin_unlock(vmf->ptl); >> >> Please make that consistent, meaning: >> >> 1) Inline __pmd_thp_fault_success_stats() into map_pmd_thp(). No need to >> have the separated out. >> >> 2) Either do the PTL unlocking in __pmd_thp_fault_success_stats() or in >>      the caller. In the caller is likely easiest. Adjusting the counters >>      should be cheap, if not we could revisit this later with real data. >> >>> + >>> +static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >>> +            struct vm_area_struct *vma, unsigned long haddr) >>> +{ >>> +    pmd_t entry; >>> + >>> +    entry = mk_huge_pmd(&folio->page, vma->vm_page_prot); >>> +    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); >>> +    folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE); >>> +    folio_add_lru_vma(folio, vma); >>> +    set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); >>> +    update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); >> >> It's quite weird to see a mixture of haddr and vmf->address, and likely >> this mixture is wrong or not not required. >> >> Looking at arc's update_mmu_cache_pmd() implementation, I cannot see how >> passing in the unaligned address would do the right thing. But maybe arc >> also doesn't trigger that code path ... who knows :) >> >> >> Staring at some other update_mmu_cache_pmd() users, it's quite >> inconsistent. Primarily only do_huge_pmd_numa_page() and >> __do_huge_pmd_anonymous_page() use the unaligned address. The others >> seem to use the aligned address ... as one would expect when modifying a >> PMD. >> >> >> I suggest to change this function to *not* pass in the vmf, and rename >> it to something like: >> >> static void folio_map_anon_pmd(struct folio *folio, struct >> vm_area_struct *vma, pmd_t *pmd, unsigned long haddr) > > ... or better "map_anon_folio_pmd" so it better matches > vma_alloc_folio_pmd() suggested above. I'll vote for this. > >