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imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=CwOdmvHG; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf09.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1794597032; b=P6Rx+wXr/7ckh7UuxjPGU/QtFInR+YWnUhvyB0J+9x4i8TBJrwTJmwPo0dNKp5oZbKvP2+ 5X2l+6O4gpofIwVIpnDGk+ZYoxszqg/XBiTrF5yH4DXhpNemdg90oUJBZMfOdaBmp4vMUQ lw2/1uA1cppuFqdTdthRm2t0noZZajs= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0428046C9C; Fri, 13 Nov 2026 19:10:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2EBA31F000C5; Fri, 13 Nov 2026 19:10:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794597031; bh=TmQhBXxYv2wy3oWjyq1yC5XpUFA1i4l5VWHKkx2FbwI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=CwOdmvHGwN0V7RevMwq+XSLErkMTQPIU0g9XgUG7+UhuxToue+GpBWcI88Yd+ek0L w7iawLFldGwkYJndnP76FS/Dpty3LMdeL+NqvKkBN4RJ3QdLt3LDhd+pfcXD3SEbC4 qzGGGJhD8QKlDJ/x4yGRZ1GHuKwM6S0LB0xIp8x7nSluJ/VguXuf//n36LJTKG6qZl Ur/t7Q0zo3zpYz2D3anxD6WcKlohv9Jc5bjpFVy6l8RSrTItGwxoH1u3D1onKQOkl0 LWfBKjrXFb8ce3frkZWzEgPc59boiD0dqbeT9b5HqX1EerJKxSsaCePcdKo+ZpFW+u OrxvUyUv6Csbg== Message-ID: <00521fb1-121d-4aef-9278-fb6b36755291@kernel.org> Date: Fri, 13 Nov 2026 20:10:26 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/ksm: add initialization helpers for scan_get_next_rmap_item() To: "Xu Xin (vivo)" Cc: chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org References: <20261112125754.176930-1-xu.xin@linux.dev> <20261112125959.177881-1-xu.xin@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20261112125959.177881-1-xu.xin@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A6E5D140012 X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: msf1s1intrwhhnkwqsbpuq8wpmpw9uaz X-HE-Tag: 1794597032-839013 X-HE-Meta: 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 jbcN6QFN sgBRL7VqpLslsrsqQYbmkf36gJqOd6yUIObgsCAwXHpLyokoNSipvAp/McO4dj3vQm0g6zbFDXJ/C3tgeLelWgJNsMEeBm9qf6PK+2gHV0+C7+Yd+nU7KXEl2zFGp1VfaaKog+tcusP/OUIBVbrOdT5cAnRWRnkQthM+bls5JsWRPzFd+Q9OungGNSY9y+kKDoU9BgcnNdAMk8Py5KngaXD6SnGlipoSaCz7E0LTr5P7/flWWYiJ5OT1sgyLB8rjXvQyxqCBJBKY6WYaCf4jYoFVZhfAOswoylTnAGX0i7Cqu6rh1BlyklaXOMg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/12/26 13:59, Xu Xin (vivo) wrote: > Extract the new scan cycle detection (including draining per-CPU LRU > caches) and advancing the scan cursor to the first mm_slot into > scan_begin_new_cycle() and scan_get_first_mm(). > > This keeps the exact execution order intact while making > scan_get_next_rmap_item() cleaner and easier to follow. > > No functional change intended. > > Signed-off-by: Xu Xin (vivo) > --- > mm/ksm.c | 70 +++++++++++++++++++++++++++++++++++++------------------- > 1 file changed, 46 insertions(+), 24 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 49977bcf04f7..e79e64372e49 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -2640,6 +2640,49 @@ static void ksm_reset_unstable_trees(void) > root_unstable_tree[nid] = RB_ROOT; > } > > +static bool scan_begin_new_cycle(void) > +{ > + /* Check if the cursor points to the head. */ > + if (ksm_scan.mm_slot != &ksm_mm_head) > + return false; > + > + /* > + * A number of pages can hang around indefinitely in per-cpu > + * LRU cache, raised page count preventing write_protect_page > + * from merging them. Though it doesn't really matter much, > + * it is puzzling to see some stuck in pages_volatile until > + * other activity jostles them out, and they also prevented > + * LTP's KSM test from succeeding deterministically; so drain > + * them here (here rather than on entry to ksm_do_scan(), > + * so we don't IPI too often when pages_to_scan is set low). > + */ > + lru_add_drain_all(); > + return true; > +} > + > +static struct ksm_mm_slot *scan_get_first_mm(void) > +{ > + struct ksm_mm_slot *mm_slot = ksm_scan.mm_slot; > + struct mm_slot *slot; > + > + spin_lock(&ksm_mmlist_lock); > + > + slot = list_entry(mm_slot->slot.mm_node.next, struct mm_slot, mm_node); > + mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); > + ksm_scan.mm_slot = mm_slot; > + > + spin_unlock(&ksm_mmlist_lock); > + > + /* > + * Although we tested list_empty() above, a racing __ksm_exit > + * of the last mm on the list may have removed it since then. > + */ > + if (mm_slot == &ksm_mm_head) > + return NULL; > + > + return mm_slot; > +} I like this function cleanup here, but not sure about the other one. Can we just leave the lru_add_drain_all() where it is, or what's the reason for that change? Note that that might soon get removed either way, so I wouldn't worry about it. Then, I would rename the function into something like "scan_should_start_new_cycle" And keep it simple. -- Cheers, David