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[2003:cb:c719:5b00:61af:900f:3aef:3af3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-362cd0d79fdsm6690117f8f.77.2024.06.20.12.38.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 12:38:22 -0700 (PDT) Message-ID: <254bf3e0-0056-4593-94ee-8431a1bfc430@redhat.com> Date: Thu, 20 Jun 2024 21:38:21 +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 v2] mm: ksm: Consider the number of ksm_mm_slot in the general_profit calculation To: Sung-hun Kim , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: sungguk.na@samsung.com, sw0312.kim@samsung.com, sebuns@gmail.com References: <20240620043914.249768-1-sfoon.kim@samsung.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: <20240620043914.249768-1-sfoon.kim@samsung.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 20.06.24 06:39, Sung-hun Kim wrote: > The current version of KSM does not take into account the number of > used ksm_mm_slot. Therefore, when users want to obtain profits of > KSM, KSM omits the memory used for allocating ksm_mm_slots. > > This patch introduces a new variable to keep track of the number of > allocated ksm_mm_slots. By doing so, KSM will be able to provide a > more accurate number of the gains made. If you take a look at the calculation explained in Documentation/admin-guide/mm/ksm.rst, we only care about rmap_items, which can grow rather substantially in size. We also don't consider other metadata, such as the size of the stable nodes etc. So why should the ksm_mm_slots matter that much that we should track them and account them? Any real life examples where this is relevant / a problem. > > Signed-off-by: Sung-hun Kim > --- > Changelog in V2: > - Add an MMF_VM_MERGEABLE flag check in ksm_process_profit for > untracked processes > --- > mm/ksm.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 34c4820e0d3d..c8ced991ccda 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -267,6 +267,9 @@ static unsigned long ksm_pages_unshared; > /* The number of rmap_items in use: to calculate pages_volatile */ > static unsigned long ksm_rmap_items; > > +/* The number of ksm_mm_slot in use */ > +static atomic_long_t ksm_mm_slots = ATOMIC_LONG_INIT(0); > + > /* The number of stable_node chains */ > static unsigned long ksm_stable_node_chains; > > @@ -1245,6 +1248,7 @@ static int unmerge_and_remove_all_rmap_items(void) > spin_unlock(&ksm_mmlist_lock); > > mm_slot_free(mm_slot_cache, mm_slot); > + atomic_long_dec(&ksm_mm_slots); > clear_bit(MMF_VM_MERGEABLE, &mm->flags); > clear_bit(MMF_VM_MERGE_ANY, &mm->flags); > mmdrop(mm); > @@ -2717,6 +2721,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) > spin_unlock(&ksm_mmlist_lock); > > mm_slot_free(mm_slot_cache, mm_slot); > + atomic_long_dec(&ksm_mm_slots); > clear_bit(MMF_VM_MERGEABLE, &mm->flags); > clear_bit(MMF_VM_MERGE_ANY, &mm->flags); > mmap_read_unlock(mm); > @@ -3000,6 +3005,7 @@ int __ksm_enter(struct mm_struct *mm) > list_add_tail(&slot->mm_node, &ksm_scan.mm_slot->slot.mm_node); > spin_unlock(&ksm_mmlist_lock); > > + atomic_long_inc(&ksm_mm_slots); > set_bit(MMF_VM_MERGEABLE, &mm->flags); > mmgrab(mm); > > @@ -3042,6 +3048,7 @@ void __ksm_exit(struct mm_struct *mm) > > if (easy_to_free) { > mm_slot_free(mm_slot_cache, mm_slot); > + atomic_long_dec(&ksm_mm_slots); > clear_bit(MMF_VM_MERGE_ANY, &mm->flags); > clear_bit(MMF_VM_MERGEABLE, &mm->flags); > mmdrop(mm); > @@ -3374,7 +3381,8 @@ static void wait_while_offlining(void) > long ksm_process_profit(struct mm_struct *mm) > { > return (long)(mm->ksm_merging_pages + mm_ksm_zero_pages(mm)) * PAGE_SIZE - > - mm->ksm_rmap_items * sizeof(struct ksm_rmap_item); > + mm->ksm_rmap_items * sizeof(struct ksm_rmap_item) - > + (test_bit(MMF_VM_MERGEABLE, &mm->flags) ? sizeof(struct ksm_mm_slot) : 0); > } > #endif /* CONFIG_PROC_FS */ > > @@ -3672,7 +3680,8 @@ static ssize_t general_profit_show(struct kobject *kobj, > long general_profit; > > general_profit = (ksm_pages_sharing + atomic_long_read(&ksm_zero_pages)) * PAGE_SIZE - > - ksm_rmap_items * sizeof(struct ksm_rmap_item); > + ksm_rmap_items * sizeof(struct ksm_rmap_item) - > + atomic_long_read(&ksm_mm_slots) * sizeof(struct ksm_mm_slot); > > return sysfs_emit(buf, "%ld\n", general_profit); > } -- Cheers, David / dhildenb