From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 594284F0525 for ; Mon, 19 Oct 2026 12:23:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792412614; cv=none; b=XV6dkLJAce9OXFG0Lpub8Icn0JZRmfeVwa65lSf3AZq1qPckxh6oaVXLGa2ibW5hbmReh6HrXi164CT5sInFcnbRAhC13HdTFsFEtJKyE7tMe+VUwnN6c0b/Rk0S3s6yohY1JEu4YE+IEa7Q6KD0QV4THe9gV7If1KAyZe1rm8c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792412614; c=relaxed/simple; bh=D/K+gtDanH7LL1oVUnqBXGxW5Q4Nl7tGMlKqfoNYBV4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OfdkW+kxqw3Zh3Tun8x2REfvz9HuLoLpgavr5jBTwTawMYrZv2+4EbU9drIvkiSFsYBsz5bha88od/4WbKvhb5clxKa1VWdxJWqNuq0F7NI/AHcJRPFLGAetiq/Mxa5uXAItm4qrab+t5pTO8R7FvD4JBX3rC2/okxAFQZc4cG8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Oq7f7u02; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Oq7f7u02" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3DAA1F000C4; Mon, 19 Oct 2026 12:23:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792412609; bh=LuiCl+I2h452P2ySjY/aKFWNJcn4drc6seXyIqCSVY8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Oq7f7u02z1MZMAwTdBQfCe7hZrRaN2XCtCDfk6Kmv9L+JzDLETnM+pXZ/QdKeAsCd IpjIT35E4EWLub8zbfJYdEvr8sZ4ATo9B3YFfoBKHidQyqWtp4k/yGXOOfSAqWKM2t QWLsVwUuEgK3krujErnkqv/z5CluTrRgy8Wb9rkHIc8/PFjdynqwnoEr0y171MeIWK Oi1QRss8lATZaL/cdyQqfX0yX/tPIMhMufaemhnMMfIWtYuzBTRhc8ASlitX1iJdCU Te16u5lGojfvFc7g8Sur8XSomaWBT9BS3Kd3isIO6Lwj9C2EWSGmMInLc1vQF14u1G R0gIBW3J68SWg== Message-ID: Date: Mon, 19 Oct 2026 14:23:21 +0200 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 RFC v2] mm: introduce copy_mc_highpages() and batch copy in folio_mc_copy() To: Pedro Falcato , Shivank Garg Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Borislav Petkov , Ankur Arora , Dave Hansen , Thomas Gleixner , Bharata B Rao , Hrushikesh Salunke , Ingo Molnar , "H . Peter Anvin" , David Laight , David Rientjes , Linus Torvalds , Teja Vojjala , Huan Nguyen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org References: <20261019-batpagecopy-v2-1-d75e7d0dfaae@amd.com> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit >> +} >> +#else >> + >> +#define COPY_MC_PAGES_NON_PREEMPT_BATCH 1 > > I would suggest that perhaps this should be the fallback for non-preemptible > models. But it gets a little weird with PREEMPT_DYNAMIC I think? Why can't we just use PROCESS_PAGES_NON_PREEMPT_BATCH where we have similar handling already? > >> + >> +static inline int copy_mc_highpages(struct page *to, struct page *from, >> + unsigned long nr_pages) >> +{ >> + unsigned long i; >> + >> + for (i = 0; i < nr_pages; i++) >> + if (copy_mc_highpage(to + i, from + i)) >> + return -EHWPOISON; >> + return 0; >> +} >> +#endif >> + >> static inline void memcpy_page(struct page *dst_page, size_t dst_off, >> struct page *src_page, size_t src_off, >> size_t len) >> diff --git a/mm/util.c b/mm/util.c >> index 7f374bb8bf36..5015cfdfeaa5 100644 >> --- a/mm/util.c >> +++ b/mm/util.c >> @@ -763,13 +763,23 @@ EXPORT_SYMBOL(folio_copy); >> >> int folio_mc_copy(struct folio *dst, struct folio *src) >> { >> - long nr = folio_nr_pages(src); >> - long i = 0; >> + const unsigned long nr_pages = folio_nr_pages(src); >> + /* >> + * Copy the largest extent possible to allow for architecture specific >> + * extent based optimizations. copy_mc_highpages() does not call >> + * cond_resched(), so limit the unit size when running under >> + * non-preemptible scheduling models. >> + */ >> + const unsigned long unit = preempt_model_preemptible() ? >> + nr_pages : COPY_MC_PAGES_NON_PREEMPT_BATCH; > > See? now mm is aware of preemption models! eww! Yeah, we have that in clear_contig_highpages() already, which is getting replicated here for copying instead of zeroing. -- Cheers, David