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[2003:cb:c708:1a00:df86:93fe:6505:d096]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36bbcf0cc83sm15510002f8f.1.2024.08.07.02.29.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Aug 2024 02:29:00 -0700 (PDT) Message-ID: Date: Wed, 7 Aug 2024 11:28:59 +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 2/2] mm: attempt to batch free swap entries for zap_pte_range() To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: justinjiang@vivo.com, chrisl@kernel.org, hughd@google.com, kaleshsingh@google.com, kasong@tencent.com, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, v-songbaohua@oppo.com, ying.huang@intel.com References: <20240807082508.358322-1-21cnbao@gmail.com> <20240807082508.358322-3-21cnbao@gmail.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: <20240807082508.358322-3-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit > mm/swapfile.c | 78 +++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 67 insertions(+), 11 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 35cb58373493..25c3f98fa8d5 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -156,6 +156,25 @@ static bool swap_is_has_cache(struct swap_info_struct *si, > return true; > } > > +static bool swap_is_last_map(struct swap_info_struct *si, > + unsigned long offset, int nr_pages, > + bool *has_cache) Please use double tabs for indenting parameters on 2nd line on new/changed code: unsigned long offset, int nr_pages, bool *has_cache) Results in less churn when renaming functions and we can frequently avoid some lines. > +{ > + unsigned char *map = si->swap_map + offset; > + unsigned char *map_end = map + nr_pages; > + bool cached = false; > + > + do { > + if ((*map & ~SWAP_HAS_CACHE) != 1) > + return false; > + if (*map & SWAP_HAS_CACHE) > + cached = true; > + } while (++map < map_end); > + > + *has_cache = cached; > + return true; > +} > + > /* > * returns number of pages in the folio that backs the swap entry. If positive, > * the folio was reclaimed. If negative, the folio was not reclaimed. If 0, no > @@ -1469,6 +1488,53 @@ static unsigned char __swap_entry_free(struct swap_info_struct *si, > return usage; > } > > +static bool __swap_entries_free(struct swap_info_struct *si, > + swp_entry_t entry, int nr) Dito. > +{ > + unsigned long offset = swp_offset(entry); > + unsigned int type = swp_type(entry); > + struct swap_cluster_info *ci; > + bool has_cache = false; > + unsigned char count; > + bool can_batch; > + int i; > + > + if (nr <= 1 || swap_count(data_race(si->swap_map[offset])) != 1) > + goto fallback; > + /* cross into another cluster */ > + if (nr > SWAPFILE_CLUSTER - offset % SWAPFILE_CLUSTER) > + goto fallback; > + > + ci = lock_cluster_or_swap_info(si, offset); > + can_batch = swap_is_last_map(si, offset, nr, &has_cache); > + if (can_batch) { > + for (i = 0; i < nr; i++) > + WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE); > + } > + unlock_cluster_or_swap_info(si, ci); > + > + if (!can_batch) > + goto fallback; I'd avoid "can_batch" and just do: ci = lock_cluster_or_swap_info(si, offset); if (!swap_is_last_map(si, offset, nr, &has_cache)) { unlock_cluster_or_swap_info(si, ci); goto fallback; } for (i = 0; i < nr; i++) WRITE_ONCE(si->swap_map[offset + i], SWAP_HAS_CACHE); unlock_cluster_or_swap_info(si, ci); > + if (!has_cache) { > + spin_lock(&si->lock); I'm no expert on that code, but we might drop the cluster lock the take the swap_info lock and then retake the cluster lock. I assume there are no races we are worrying about here, right? > + swap_entry_range_free(si, entry, nr); > + spin_unlock(&si->lock); > + } > + return has_cache; > + > +fallback: > + for (i = 0; i < nr; i++) { One space too much before the "<". > + if (data_race(si->swap_map[offset + i])) { > + count = __swap_entry_free(si, swp_entry(type, offset + i)); > + if (count == SWAP_HAS_CACHE) > + has_cache = true; > + } else { > + WARN_ON_ONCE(1); > + } > + } > + return has_cache; > +} > + -- Cheers, David / dhildenb