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b=uPQqcGe/EGy5lWnJqkZWi9fwwkiM+npLlNc5o6t9JHt8I7qt32P7g3SrzVJGz5g7fhoF/h3jrKLy3BuJ5M21EKslv82p4Q75H0ACLRJGw4AHJnn9iX54x0siaaQ0Z3KDfW1XM2C1v0MP4gFiJPF0R9ilg+HFFZG2QUaWWkw2cH0= Received: from 30.74.144.116(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WjZl5p9_1753242451 cluster:ay36) by smtp.aliyun-inc.com; Wed, 23 Jul 2025 11:47:32 +0800 Message-ID: <65476b79-e493-4f09-ab6b-3748ab679429@linux.alibaba.com> Date: Wed, 23 Jul 2025 11:47:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] khugepaged: Optimize collapse_pte_mapped_thp() by PTE batching To: Dev Jain , akpm@linux-foundation.org, david@redhat.com Cc: ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250722150559.96465-1-dev.jain@arm.com> <20250722150559.96465-4-dev.jain@arm.com> From: Baolin Wang In-Reply-To: <20250722150559.96465-4-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A2F8540007 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: bsrc8gso1nk13mptu77trfbxnok953id X-HE-Tag: 1753242457-578707 X-HE-Meta: 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 GRAs32sP n6DbqeNppZ9/EtTMm/Dv1SWacR7rRogItIZwD94zsL4tvfFqp7SgGUWAdRjmTyEXgFc0YPmrZbv5ZzdMaS1y5Vjmhf68vBNpfvMcVRzfZH2tlYq/Dtai3pLt4mU+ooHqa8ozc756QcQd3B6KHNRdYKTR/xurmj6vQFnfJl11//E4TLxDlxFGvmpWAZKYs1VLP06OtcTtKYW07WUbabTkU4y13QZmRa+mecK3nSh1Aph007qTGFiNtHIECrZL7mmFIqumhB7Lxttd/etE1HMITL/xk8LlW7V92FNeEXGIgXdgSGvxeXWPy+XF3NQrvRuD1ebGZ60l8yUgXGlS6PYx+konGvmoQ1N+E6aHZb0txzU8CzvV2aYrOjzke1A== 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 2025/7/22 23:05, Dev Jain wrote: > Use PTE batching to optimize collapse_pte_mapped_thp(). > > On arm64, suppose khugepaged is scanning a pte-mapped 2MB THP for collapse. > Then, calling ptep_clear() for every pte will cause a TLB flush for every > contpte block. Instead, clear_ptes() does a contpte_try_unfold_partial() > which will flush the TLB only for the (if any) starting and ending contpte > block, if they partially overlap with the range khugepaged is looking at. > > For all arches, there should be a benefit due to batching atomic operations > on mapcounts due to folio_remove_rmap_ptes() and saving some calls. > > Note that we do not need to make a change to the check > "if (folio_page(folio, i) != page)"; if i'th page of the folio is equal > to the first page of our batch, then i + 1, .... i + nr_batch_ptes - 1 > pages of the folio will be equal to the corresponding pages of our > batch mapping consecutive pages. > > Signed-off-by: Dev Jain With David's comments addressed, LGTM. Thanks. Reviewed-by: Baolin Wang