From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 E38303D72 for ; Mon, 1 Jul 2024 14:03:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842588; cv=none; b=bMPVVtSPJFfhdIHqKV1RaSAVxS8fnzrzx66EirFphwQosJXdxNgyJcllOyDGgwtKdLeYGYWeuGExRI8ciP7da8Il0RpKI1B0410k+op3XF8zyWznTZaaBej6erPZ6e5I/gSNJkQn4llHEOphDz8fhPMM3WAeOatASm87WDFjck0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842588; c=relaxed/simple; bh=/TgANefb4fndSMvSkJ7LU/0RsV+LcQn3Ng+3b9MaRxY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=REQJFkfBjY4hQr4W2mcrEnnGczWdU2lWQlDdCT0+mB6UGd2ZH/JE6ar6bd36pBxxvNXnR9xNjbsBuMECDMfBfHLtl3miaseQKIHFgFuFMpcTcIH5kjL84+SIwx7l9ZV07dQHZ6MA5L65RqgjbaYcWB6W9fF5+ENYadcmRCQyL88= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=gSh7zZPP; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gSh7zZPP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719842585; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=61mGJpiLpxwzl0cKLTanEmOAKYFVvvHzMnnjtuUoHyE=; b=gSh7zZPP84aF9yVGPMudLtqMYYwwKXj/RXcf3yL+uwSG0eR3F89q4lcxdqUUaWi3AR1Iqj 5QAYqcrsOaA+KcY/888giyBLiTfqdL4MUl+EisWNlAoyjIwBBe1qONzrJHG2dN2RxO3OOO VOjUbRLvTAsQjstAnhckDu+fpzK6EM0= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-360-PSxv4IRYOhmmKw_H0mjGuw-1; Mon, 01 Jul 2024 10:03:04 -0400 X-MC-Unique: PSxv4IRYOhmmKw_H0mjGuw-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-36248c176c4so2075410f8f.1 for ; Mon, 01 Jul 2024 07:03:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719842583; x=1720447383; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=61mGJpiLpxwzl0cKLTanEmOAKYFVvvHzMnnjtuUoHyE=; b=rIZZX77y8+ji2cYKsi9oAegos9mWdRITyZZW/cJh3/v3G5BW4doBS+4JJDVX8EB6Z8 gXJSvE7BQDPqPKFjjqfKViYinxRGlvvFFUU4PF2PkcxOpSPlkT++6wE4t+J4f3mWT2Yq zVwnBmETJwZOLy6guqr6VumsaN4s8VH+hm+vO0mijSMkYvxciTvvfWscTPKpgyZuFBPq Rj9FOqfZqHJ4E6aU3/gWe+ar4tykoKPkc3zA6CBmP0Q9wgv86N045EjHqlNnSkjeUVYv jJ/aVx7fVBYi5SnBe/npMkNikvllyRvNEB09HhnOziGd1w7yLXpqrDH7pY7MmFUipltm ohzg== X-Gm-Message-State: AOJu0YxMROvD+Ah0gFwihTYZJX9QP8ormuJkpqNaGryeO8wQPC3K26TU TPmTXYLmMzdFPS6zJSyIYO8Z6qDNLMM5j2uV0W+AlwQ53cmi47A3/bP5HFuOdd6QKpHplfWzAVk ChrDtRQmOH7g9Okv1NgLYdizopO9Bsr8iL6FTSARyuNeB/XDXI5uhd6CvUeqj3g== X-Received: by 2002:a5d:6a02:0:b0:35f:1d10:18f0 with SMTP id ffacd0b85a97d-367757285admr2845092f8f.64.1719842583056; Mon, 01 Jul 2024 07:03:03 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHNJHVvRIHudS6QMF5kyklF0UxeLVMjv88XUXoAURf12mPcQi+jX7ThfbVuT17C3VBBTR9tng== X-Received: by 2002:a5d:6a02:0:b0:35f:1d10:18f0 with SMTP id ffacd0b85a97d-367757285admr2845072f8f.64.1719842582552; Mon, 01 Jul 2024 07:03:02 -0700 (PDT) Received: from ?IPV6:2a01:599:920:8ca1:a0b5:9e51:26ba:6a2b? ([2a01:599:920:8ca1:a0b5:9e51:26ba:6a2b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3675a0d9f9dsm10098082f8f.41.2024.07.01.07.03.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 07:03:01 -0700 (PDT) Message-ID: Date: Mon, 1 Jul 2024 16:03:00 +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 v1 2/2] mm/migrate: move NUMA hinting fault folio isolation + checks under PTL To: Zi Yan , "Huang, Ying" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton References: <20240620212935.656243-1-david@redhat.com> <20240620212935.656243-3-david@redhat.com> <0F4ABC1D-7A26-4AE2-BCAA-3EA906FB13A7@nvidia.com> <9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com> <87ed8do6kl.fsf@yhuang6-desk2.ccr.corp.intel.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 01.07.24 15:50, Zi Yan wrote: > On 1 Jul 2024, at 4:32, Huang, Ying wrote: > >> "Zi Yan" writes: >> >>> On Wed Jun 26, 2024 at 12:49 PM EDT, David Hildenbrand wrote: >>>> On 21.06.24 22:48, Zi Yan wrote: >>>>> On 21 Jun 2024, at 16:18, David Hildenbrand wrote: >>>>> >>>>>> On 21.06.24 15:44, Zi Yan wrote: >>>>>>> On 20 Jun 2024, at 17:29, David Hildenbrand wrote: >>>>>>> >>>>>>>> Currently we always take a folio reference even if migration will not >>>>>>>> even be tried or isolation failed, requiring us to grab+drop an additional >>>>>>>> reference. >>>>>>>> >>>>>>>> Further, we end up calling folio_likely_mapped_shared() while the folio >>>>>>>> might have already been unmapped, because after we dropped the PTL, that >>>>>>>> can easily happen. We want to stop touching mapcounts and friends from >>>>>>>> such context, and only call folio_likely_mapped_shared() while the folio >>>>>>>> is still mapped: mapcount information is pretty much stale and unreliable >>>>>>>> otherwise. >>>>>>>> >>>>>>>> So let's move checks into numamigrate_isolate_folio(), rename that >>>>>>>> function to migrate_misplaced_folio_prepare(), and call that function >>>>>>>> from callsites where we call migrate_misplaced_folio(), but still with >>>>>>>> the PTL held. >>>>>>>> >>>>>>>> We can now stop taking temporary folio references, and really only take >>>>>>>> a reference if folio isolation succeeded. Doing the >>>>>>>> folio_likely_mapped_shared() + golio isolation under PT lock is now similar >>>>>>>> to how we handle MADV_PAGEOUT. >>>>>>>> >>>>>>>> While at it, combine the folio_is_file_lru() checks. >>>>>>>> >>>>>>>> Signed-off-by: David Hildenbrand >>>>>>>> --- >>>>>>>> include/linux/migrate.h | 7 ++++ >>>>>>>> mm/huge_memory.c | 8 ++-- >>>>>>>> mm/memory.c | 9 +++-- >>>>>>>> mm/migrate.c | 81 +++++++++++++++++++---------------------- >>>>>>>> 4 files changed, 55 insertions(+), 50 deletions(-) >>>>>>> >>>>>>> LGTM. Reviewed-by: Zi Yan >>>>>>> >>>>>>> One nit below: >>>>>>> >>>>>>> >>>>>>> >>>>>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>>>>>> index fc27dabcd8e3..4b2817bb2c7d 100644 >>>>>>>> --- a/mm/huge_memory.c >>>>>>>> +++ b/mm/huge_memory.c >>>>>>>> @@ -1688,11 +1688,13 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) >>>>>>>> if (node_is_toptier(nid)) >>>>>>>> last_cpupid = folio_last_cpupid(folio); >>>>>>>> target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags); >>>>>>>> - if (target_nid == NUMA_NO_NODE) { >>>>>>>> - folio_put(folio); >>>>>>>> + if (target_nid == NUMA_NO_NODE) >>>>>>>> + goto out_map; >>>>>>>> + if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) { >>>>>>>> + flags |= TNF_MIGRATE_FAIL; >>>>>>>> goto out_map; >>>>>>>> } >>>>>>>> - >>>>>>>> + /* The folio is isolated and isolation code holds a folio reference. */ >>>>>>>> spin_unlock(vmf->ptl); >>>>>>>> writable = false; >>>>>>>> >>>>>>>> diff --git a/mm/memory.c b/mm/memory.c >>>>>>>> index 118660de5bcc..4fd1ecfced4d 100644 >>>>>>>> --- a/mm/memory.c >>>>>>>> +++ b/mm/memory.c >>>>>>> >>>>>>> >>>>>>> >>>>>>>> @@ -5345,10 +5343,13 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >>>>>>>> else >>>>>>>> last_cpupid = folio_last_cpupid(folio); >>>>>>>> target_nid = numa_migrate_prep(folio, vmf, vmf->address, nid, &flags); >>>>>>>> - if (target_nid == NUMA_NO_NODE) { >>>>>>>> - folio_put(folio); >>>>>>>> + if (target_nid == NUMA_NO_NODE) >>>>>>>> + goto out_map; >>>>>>>> + if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) { >>>>>>>> + flags |= TNF_MIGRATE_FAIL; >>>>>>>> goto out_map; >>>>>>>> } >>>>>>> >>>>>>> These two locations are repeated code, maybe just merge the ifs into >>>>>>> numa_migrate_prep(). Feel free to ignore if you are not going to send >>>>>>> another version. :) >>>>>> >>>>>> I went back and forth a couple of times and >>>>>> >>>>>> a) Didn't want to move numa_migrate_prep() into >>>>>> migrate_misplaced_folio_prepare(), because having that code in >>>>>> mm/migrate.c felt a bit odd. >>>>> >>>>> I agree after checking the actual code, since the code is just >>>>> updating NUMA fault stats and checking where the folio should be. >>>>> >>>>>> >>>>>> b) Didn't want to move migrate_misplaced_folio_prepare() because I enjoy >>>>>> seeing the migrate_misplaced_folio_prepare() and >>>>>> migrate_misplaced_folio() calls in the same callercontext. >>>>>> >>>>>> I also considered renaming numa_migrate_prep(), but wasn't really able to come up with a good name. >>>>> >>>>> How about numa_migrate_check()? Since it tells whether a folio should be >>>>> migrated or not. >>>>> >>>>>> >>>>>> But maybe a) is not too bad? >>>>>> >>>>>> We'd have migrate_misplaced_folio_prepare() consume &flags and &target_nid, and perform the "flags |= TNF_MIGRATE_FAIL;" internally. >>>>>> >>>>>> What would be your take? >>>>> >>>>> I would either rename numa_migrate_prep() or just do nothing. I have to admit >>>>> that the "prep" and "prepare" in both function names motivated me to propose >>>>> the merge, but now the actual code tells me they should be separate. >>>> >>>> Let's leave it like that for now. Renaming to numa_migrate_check() makes >>>> sense, and likely moving more numa handling stuff in there. >>>> >>>> Bit I yet have to figure out why some of the memory.c vs. huge_memory.c >>>> code differences exist, so we can unify them. >>>> >>>> For example, why did 33024536bafd9 introduce slightly different >>>> last_cpupid handling in do_huge_pmd_numa_page(), whereby it seems like >>>> some subtle difference in handling NUMA_BALANCING_MEMORY_TIERING? Maybe >>>> I am missing something obvious. :) >>> >>> It seems to me that a sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING >>> check is missing in do_huge_pmd_numa_page(). So the >>> >>> if (node_is_toptier(nid)) >>> >>> should be >>> >>> if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) || >>> node_is_toptier(nid)) >>> >>> to be consistent with other checks. Add Ying to confirm. >> >> Yes. It should be so. Sorry for my mistake and confusing. > > Thank you for the confirmation. > >> >>> I also think a function like >>> >>> bool folio_has_cpupid(folio) >>> { >>> return !(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) >>> || node_is_toptier(folio_nid(folio)); >>> } >>> >>> would be better than the existing checks. >> >> Yes. This looks better. Even better, we can add some comments to the >> function too. > > I will prepare a patch about it. Do you have capacity to further consolidate the logic, maybe moving more stuff into the numa_migrate_prep (and renaming it? :)). -- Cheers, David / dhildenb