From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794597032; b=pRB6M7ajXAK18DJHhLVKtGWyxD2OlOrSsqwBAs4CNP/eU3r7pCxephbHpfmPHr/9vZvz bDFiQDAskc0Ag6peO7WqjKYjn3ZmpGwQDzBYySj59TsT49ad6SbCN6S5RJYk9CnBw6Pmq kK0mgC9FNo2npHnvckQaUjXb66vaID73sKjandHlDGaaBqFV89/sPdkTBBz/yhNMlc12v agG9RIpctkzoHje7y8YyBkF5g4dvCgtB+Ds6k26x+42h5kysBdYVsg+8umGXQszNOMCTc 3bgcuxwb3yPGLGkHaaarqa6q5CYw4JRqUiV2KJ9WaXJS1Qy4sDJi6HxBYTejfeKKQSw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794597032; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=TmQhBXxYv2wy3oWjyq1yC5XpUFA1i4l5VWHKkx2FbwI=; b=xvKuXUPNuWxzybfDGlBDmBz2+A/9llXVj8YVWjn619Z1bb831CNWK4zwFI+Zw8Ty1G1E UO8SwwCEfZgxAzdA/7zA0fPJEPBX2LjBxVe8EGwLDfnZF2pTClp7stpxrUz8q7rqzJfJr gij0oQH4mPMAps9y8Ygc7CT9sCjK9bVl9B/SKaLzwh9zoefe2lpQiLDG5qZO/j/ihMFUo L2CvZMR+dEVe120eM4KQ987Y1QBghHqmcszzPDu98CEmSEJ/Ay19whB/F8wXe/hYSItHx cdlhKcF5BDemz0owPeJZyt1dkxyXKlKHAovBHGg+QLHslJ+vl9XuNorWtVE8hDiGF7Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CwOdmvHG; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40B20606A33D for ; Fri, 13 Nov 2026 19:10:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CwOdmvHG 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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 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