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 2AF24535D4 for ; Mon, 1 Jul 2024 12:21:10 +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=1719836474; cv=none; b=eGjeNNAXq7ztoVNhXvdqDopyQllObW+B8t+o0cnjrWosyimhIdFLvzDayjHCXg7rwrtAJcE3Xwa0b/dLPPpS9GAQaZIukd/+biIcOTpPkMBHgNR5Mh1///02CXjgo5K0LR2jzSm4gdriCrhqRUmrfzAqyDv9kvxPJDxv67chSu4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719836474; c=relaxed/simple; bh=/6Gd1ZwDFUNnMJ2uBMguuhnDYkcN1O3JID9bz1oDBaQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Gctb8hlA/o8k7IxrO/4fB0YTybE5VZhsLJIveDZdzwvXbir8vjHoSJw2OeeQZYzq3R6R+GZC7vQLeBK2jaLR1GYnN+4yMMnYJiJRTdfTrO03Fw/Gn5aS8sgva7KyRJ1KaTayytz+8EJU24ua2FhjXSdpjJG/5W8TQVPGM2hxzP8= 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=cmZ9Yygl; 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="cmZ9Yygl" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719836469; 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=b4cr2TJUSOX8psrkisRLH0Pv2Sv8xCK0gi7iHprkIpc=; b=cmZ9YyglI7u9CrhBtpU3wmfX9bDSWgcrtf4AVj0TlB8y8FhFt7RLOVSJUOM4gBx25N7zKw 7ZePczN2EvgIoV//9EVExTnfhuFLOrYkXs4vrnKbOhNEQDxpb1lm00ag7NyAHTgm0gb6Lh eqbsv2orrzEB6LNbprLPdEHsqBIuw9s= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-80-b_tuKr2nNX6-TRwdbz9xDw-1; Mon, 01 Jul 2024 08:21:08 -0400 X-MC-Unique: b_tuKr2nNX6-TRwdbz9xDw-1 Received: by mail-ed1-f71.google.com with SMTP id 4fb4d7f45d1cf-57d4769a15bso118590a12.1 for ; Mon, 01 Jul 2024 05:21:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719836467; x=1720441267; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :content-language: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=b4cr2TJUSOX8psrkisRLH0Pv2Sv8xCK0gi7iHprkIpc=; b=hHRhxjkvdFuioSjSg17kClSTCEfxCWuld6cI35FXQWRVL4/WDNzlCcJ0d5DknSTXHO JGmI2w0fmCca2DWOjcPppY1L8/d6WTfr2gNWNlnXVxgFZNr6coFw+8IcJLWeyQOZSC83 TAsktnyrabmHTDgPS7zOZsO0GKhOnpLV7FYdLBJMilbfCYTYHOceVA1h37uqKSmNqv/l MxU1SaGYSnHQGfuAiz096OM7urlj2nZzS1U7vqN067EZImiQekf24NmsNTM7adVe/ShQ wGlFI0XtmJEtX8uamAIIjGMqT7XSauKIIDaZ1KBPPW5r6fGPibtx1g4dQ7IQHkEC5fjG Ovow== X-Forwarded-Encrypted: i=1; AJvYcCWr3kVbSg7PmLNWy3dqehHY/MincO9kGwQYfeL2OLiXaBFdUpeGgUCNno39wpxjfuLKlWO8hHhXb860ktIK4gLlVo+n1QPttQNUGwFU X-Gm-Message-State: AOJu0YzmSDEsiMQhqPUeA7BYn9H97S1CraBVJ95iwR7n/64IMVb2hPyn hPoeDJ1BmBNg0HXefA6c3k44Ry7/dT5ViUUqN5IfmjscALpNkMxJq7+dVxIvn+1MCjsR5F8kBu6 cG8HZKIaDwzSRsdU7oyVukQdABKjyCjg5j6buzjwWN0o1yWSKrPOAzhM0Nxia8wHzofpj5Q== X-Received: by 2002:a05:6402:430b:b0:57c:74ea:8d24 with SMTP id 4fb4d7f45d1cf-5879f59c5b7mr3456402a12.18.1719836467102; Mon, 01 Jul 2024 05:21:07 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHo1yMsMqgOwRI2CFdsiZqrPuVLonQmuF2KUrgdc7gWtsaEuOBrvmzPVL/EsEo/QBjfoWKUaA== X-Received: by 2002:a05:6402:430b:b0:57c:74ea:8d24 with SMTP id 4fb4d7f45d1cf-5879f59c5b7mr3456390a12.18.1719836466583; Mon, 01 Jul 2024 05:21:06 -0700 (PDT) Received: from [100.81.188.195] (ipb218f94c.dynamic.kabel-deutschland.de. [178.24.249.76]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-586138185ebsm4352302a12.52.2024.07.01.05.21.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 05:21:06 -0700 (PDT) Message-ID: Date: Mon, 1 Jul 2024 14:21:05 +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 1/2] mm: add per-order mTHP split counters To: Barry Song Cc: Ryan Roberts , Lance Yang , akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240424135148.30422-1-ioworker0@gmail.com> <20240424135148.30422-2-ioworker0@gmail.com> <23d9f708-b1fd-4b10-b755-b7ef6aa683e8@redhat.com> Content-Language: en-US From: David Hildenbrand 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: 8bit On 01.07.24 13:43, Barry Song wrote: > On Mon, Jul 1, 2024 at 8:56 PM David Hildenbrand wrote: >> >> On 30.06.24 11:48, Barry Song wrote: >>> On Thu, Apr 25, 2024 at 3:41 AM Ryan Roberts wrote: >>>> >>>> + Barry >>>> >>>> On 24/04/2024 14:51, Lance Yang wrote: >>>>> At present, the split counters in THP statistics no longer include >>>>> PTE-mapped mTHP. Therefore, this commit introduces per-order mTHP split >>>>> counters to monitor the frequency of mTHP splits. This will assist >>>>> developers in better analyzing and optimizing system performance. >>>>> >>>>> /sys/kernel/mm/transparent_hugepage/hugepages-/stats >>>>> split_page >>>>> split_page_failed >>>>> deferred_split_page >>>>> >>>>> Signed-off-by: Lance Yang >>>>> --- >>>>> include/linux/huge_mm.h | 3 +++ >>>>> mm/huge_memory.c | 14 ++++++++++++-- >>>>> 2 files changed, 15 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>>>> index 56c7ea73090b..7b9c6590e1f7 100644 >>>>> --- a/include/linux/huge_mm.h >>>>> +++ b/include/linux/huge_mm.h >>>>> @@ -272,6 +272,9 @@ enum mthp_stat_item { >>>>> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE, >>>>> MTHP_STAT_ANON_SWPOUT, >>>>> MTHP_STAT_ANON_SWPOUT_FALLBACK, >>>>> + MTHP_STAT_SPLIT_PAGE, >>>>> + MTHP_STAT_SPLIT_PAGE_FAILED, >>>>> + MTHP_STAT_DEFERRED_SPLIT_PAGE, >>>>> __MTHP_STAT_COUNT >>>>> }; >>>>> >>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>>> index 055df5aac7c3..52db888e47a6 100644 >>>>> --- a/mm/huge_memory.c >>>>> +++ b/mm/huge_memory.c >>>>> @@ -557,6 +557,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK); >>>>> DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); >>>>> DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT); >>>>> DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK); >>>>> +DEFINE_MTHP_STAT_ATTR(split_page, MTHP_STAT_SPLIT_PAGE); >>>>> +DEFINE_MTHP_STAT_ATTR(split_page_failed, MTHP_STAT_SPLIT_PAGE_FAILED); >>>>> +DEFINE_MTHP_STAT_ATTR(deferred_split_page, MTHP_STAT_DEFERRED_SPLIT_PAGE); >>>>> >>>>> static struct attribute *stats_attrs[] = { >>>>> &anon_fault_alloc_attr.attr, >>>>> @@ -564,6 +567,9 @@ static struct attribute *stats_attrs[] = { >>>>> &anon_fault_fallback_charge_attr.attr, >>>>> &anon_swpout_attr.attr, >>>>> &anon_swpout_fallback_attr.attr, >>>>> + &split_page_attr.attr, >>>>> + &split_page_failed_attr.attr, >>>>> + &deferred_split_page_attr.attr, >>>>> NULL, >>>>> }; >>>>> >>>>> @@ -3083,7 +3089,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, >>>>> XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order); >>>>> struct anon_vma *anon_vma = NULL; >>>>> struct address_space *mapping = NULL; >>>>> - bool is_thp = folio_test_pmd_mappable(folio); >>>>> + int order = folio_order(folio); >>>>> int extra_pins, ret; >>>>> pgoff_t end; >>>>> bool is_hzp; >>>>> @@ -3262,8 +3268,10 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, >>>>> i_mmap_unlock_read(mapping); >>>>> out: >>>>> xas_destroy(&xas); >>>>> - if (is_thp) >>>>> + if (order >= HPAGE_PMD_ORDER) >>>>> count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); >>>>> + count_mthp_stat(order, !ret ? MTHP_STAT_SPLIT_PAGE : >>>>> + MTHP_STAT_SPLIT_PAGE_FAILED); >>>>> return ret; >>>>> } >>>>> >>>>> @@ -3327,6 +3335,8 @@ void deferred_split_folio(struct folio *folio) >>>>> if (list_empty(&folio->_deferred_list)) { >>>>> if (folio_test_pmd_mappable(folio)) >>>>> count_vm_event(THP_DEFERRED_SPLIT_PAGE); >>>>> + count_mthp_stat(folio_order(folio), >>>>> + MTHP_STAT_DEFERRED_SPLIT_PAGE); >>>> >>>> There is a very long conversation with Barry about adding a 'global "mTHP became >>>> partially mapped 1 or more processes" counter (inc only)', which terminates at >>>> [1]. There is a lot of discussion about the required semantics around the need >>>> for partial map to cover alignment and contiguity as well as whether all pages >>>> are mapped, and to trigger once it becomes partial in at least 1 process. >>>> >>>> MTHP_STAT_DEFERRED_SPLIT_PAGE is giving much simpler semantics, but less >>>> information as a result. Barry, what's your view here? I'm guessing this doesn't >>>> quite solve what you are looking for? >>> >>> This doesn't quite solve what I am looking for but I still think the >>> patch has its value. >>> >>> I'm looking for a solution that can: >>> >>> * Count the amount of memory in the system for each mTHP size. >>> * Determine how much memory for each mTHP size is partially unmapped. >>> >>> For example, in a system with 16GB of memory, we might find that we have 3GB >>> of 64KB mTHP, and within that, 512MB is partially unmapped, potentially wasting >>> memory at this moment. I'm uncertain whether Lance is interested in >>> this job :-) >>> >>> Counting deferred_split remains valuable as it can signal whether the system is >>> experiencing significant partial unmapping. >> >> I'll note that, especially without subpage mapcounts, in the future we >> won't have that information (how much is currently mapped) readily >> available in all cases. To obtain that information on demand, we'd have >> to scan page tables or walk the rmap. > > I'd like to keep things simple. We can ignore the details about how > the folio is partially > unmapped. For example, whether 15 out of 16 subpages are unmapped or just 1 is > unmapped doesn't matter. When we add a folio to the deferred_list, we > increase the > count by 1. When we remove a folio from the deferred_list (for any > reason, such as > a real split), we decrease the count by 1. Yes, that's valuable and not too complicated. -- Cheers, David / dhildenb