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 15D59531AF0 for ; Wed, 23 Sep 2026 13:19:47 +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=1790169601; cv=none; b=dhs48Khb4aAHLQ9K/Sn6fb/WINzKROPY6Z+N+ZLpjSYyn3TiPOmfCW5nYibFQRgAQ0mIZ0E/G5o4IctV6QdmiGzT2/iMKEWTAkXRbptPlpRqCLoudeu77xjjdtfspnrRD0F3ct+CyiFxYQPu/fztBItfiuKOAGcP0woTuYjcBds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790169601; c=relaxed/simple; bh=OjWXPIvLNc6n7/N3/PTFzOrtR0JqXSNHicvsujdPpKw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QUfFQTq+9tr78IskacV1ZqnhOA2zN27C+VO/6ANATc/nD65o/d6aD68iJm3Sw03uDvWqbZJP6m9pFJTvI2eQUKcTnAO7pF985tWMtZpsiKMi5H4utKMJ6oGselb/DlCMim+R4FDcPfe6QhSW3j1IUS+91h6Rz+k7uvZGiqmAW+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i1/H3BIw; 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="i1/H3BIw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 691C01F000FF; Wed, 23 Sep 2026 13:19:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790169584; bh=1yeMMNYYq0MjqSUEKuIfnViLoDuHUncMTKA/2pebiVA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=i1/H3BIwXC/3FqxM7OhmXImiWOFFXzO19DqjayzdfQFmlHNTwKnf8kEd4Ouqi18fB sQitBw2loeZ18GwUJs7owPN4iXTEXiDzc2I9ck5KYzrNt6VQ+cK/COu3qu+1+fVnMR mgMeReDp73bHZwF8HeiycWMDG44daShEsWqUyfx98HxGZFIcb6ptUVcBPPVfRXQ2mL xyFDkkiIvutmfJeR5AEQG/ZWhqP4kC8weztIKGKg5XnVO6J7Mwnmnpl4ONvhAfF9th zJf/X4dslfJzXVHvTjR1WSlX6y/OpSVHCP6pW/8rRz+/PUByPnUwffhruLZo3qCoQx NJOL7TqR2mNig== Message-ID: Date: Wed, 23 Sep 2026 15:19:36 +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 v3 10/12] mm/collapse: work out the orders a VMA allows once per VMA To: Kiryl Shutsemau , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang Cc: "Kiryl Shutsemau (Meta)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Jann Horn References: <20260916093145.4022188-1-kirill@shutemov.name> <20260916093145.4022188-11-kirill@shutemov.name> 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: <20260916093145.4022188-11-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/16/26 11:31, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > The scan asked collapse_possible_orders() for every PTE table, for an > answer that is a property of the VMA. Both callers walk a VMA a table at > a time, so let them work it out once and pass the mask in. It is only > good while the lock that produced it is held, so madvise_collapse() takes > it again after every collapse. > > The mask is then sampled once per VMA rather than once per table. A thp > enabled knob written during a walk takes effect one VMA later, and cannot > widen a collapse: hugepage_vma_revalidate() tests the order again under > the lock the collapse retakes. > > Assisted-by: LLM > Reviewed-by: Zi Yan > Reviewed-by: Baolin Wang > Signed-off-by: Kiryl Shutsemau (Meta) > --- > mm/khugepaged.c | 32 ++++++++++++++++++-------------- > 1 file changed, 18 insertions(+), 14 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 9e6b2af6519e..12cb67d8df32 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1549,12 +1549,12 @@ static enum scan_result mthp_collapse(struct mm_struct *mm, unsigned long addres > } > [...] > + /* One mask for the whole VMA */ > + orders = collapse_possible_orders(vma, vma->vm_flags, > + cc->policy.tva_type); cc->policy.tva_type is always sattic here, no? > + if (!orders) { > cc->progress++; > continue; > } > @@ -2922,7 +2922,7 @@ static void collapse_scan_mm_slot(unsigned int progress_max, > /* move to next address */ > khugepaged_scan.address += HPAGE_PMD_SIZE; > > - *result = collapse_scan_pmd(vma, addr, cc); > + *result = collapse_scan_pmd(vma, addr, cc, orders); > /* Nothing to do here, and the lock is still ours */ > if (*result != SCAN_SUCCEED && > *result != SCAN_PTE_MAPPED_HUGEPAGE) { > @@ -3207,14 +3207,16 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, > { > struct collapse_control *cc; > struct mm_struct *mm = vma->vm_mm; > - unsigned long hstart, hend, addr; > + unsigned long hstart, hend, addr, orders; > enum scan_result last_fail = SCAN_FAIL; > int thps = 0; > > BUG_ON(vma->vm_start > start); > BUG_ON(vma->vm_end < end); > > - if (!collapse_possible_orders(vma, vma->vm_flags, TVA_FORCED_COLLAPSE)) > + orders = collapse_possible_orders(vma, vma->vm_flags, > + TVA_FORCED_COLLAPSE); > + if (!orders) > return -EINVAL; > > hstart = ALIGN(start, HPAGE_PMD_SIZE); > @@ -3252,9 +3254,11 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, > } > vma = found; > hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); > + orders = collapse_possible_orders(vma, vma->vm_flags, > + cc->policy.tva_type); That's always TVA_FORCED_COLLAPSE, no? It's a shame we cannot get rid of cc->policy.tva_type because we need it for hugepage_vma_revalidate to calculate orders. Which sucks a bit. -- Cheers, David