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[2003:cb:c708:1500:d584:7ad8:d3f7:5539]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-432d55417f3sm21648285e9.34.2024.11.13.03.43.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Nov 2024 03:43:31 -0800 (PST) Message-ID: <6e9c649f-5fc9-4fcc-928c-c4f46a74ca66@redhat.com> Date: Wed, 13 Nov 2024 12:43:29 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/7] mm: introduce do_zap_pte_range() To: Qi Zheng Cc: jannh@google.com, hughd@google.com, willy@infradead.org, mgorman@suse.de, muchun.song@linux.dev, vbabka@kernel.org, akpm@linux-foundation.org, zokeefe@google.com, rientjes@google.com, peterx@redhat.com, catalin.marinas@arm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org References: <1639ac32194f2b2590852f410fd3ce3595eb730b.1730360798.git.zhengqi.arch@bytedance.com> <2fd11f54-8c0c-401d-8635-e54ebf7facc2@bytedance.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 13.11.24 03:40, Qi Zheng wrote: > > > On 2024/11/13 01:00, David Hildenbrand wrote: >> On 31.10.24 09:13, Qi Zheng wrote: >>> This commit introduces do_zap_pte_range() to actually zap the PTEs, which >>> will help improve code readability and facilitate secondary checking of >>> the processed PTEs in the future. >>> >>> No functional change. >>> >>> Signed-off-by: Qi Zheng >>> --- >>>   mm/memory.c | 45 ++++++++++++++++++++++++++------------------- >>>   1 file changed, 26 insertions(+), 19 deletions(-) >>> >>> diff --git a/mm/memory.c b/mm/memory.c >>> index bd9ebe0f4471f..c1150e62dd073 100644 >>> --- a/mm/memory.c >>> +++ b/mm/memory.c >>> @@ -1657,6 +1657,27 @@ static inline int zap_nonpresent_ptes(struct >>> mmu_gather *tlb, >>>       return nr; >>>   } >>> +static inline int do_zap_pte_range(struct mmu_gather *tlb, >>> +                   struct vm_area_struct *vma, pte_t *pte, >>> +                   unsigned long addr, unsigned long end, >>> +                   struct zap_details *details, int *rss, >>> +                   bool *force_flush, bool *force_break) >>> +{ >>> +    pte_t ptent = ptep_get(pte); >>> +    int max_nr = (end - addr) / PAGE_SIZE; >>> + >>> +    if (pte_none(ptent)) >>> +        return 1; >> >> Maybe we should just skip all applicable pte_none() here directly. > > Do you mean we should keep pte_none() case in zap_pte_range()? Like > below: > No rather an addon patch that will simply skip over all consecutive pte_none, like: if (pte_none(ptent)) { int nr; for (nr = 1; nr < max_nr; nr++) { ptent = ptep_get(pte + nr); if (pte_none(ptent)) continue; } max_nr -= nr; if (!max_nr) return nr; addr += nr * PAGE_SIZE; pte += nr; } Assuming that it's likely more common to have larger pte_none() holes that single ones, optimizing out the need_resched()+force_break+incremental pte/addr increments etc. -- Cheers, David / dhildenb