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Thu, 10 Apr 2025 22:04:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEuHd5b/4/FiYUP9OhKyCUlRjGkb1liUBaCYJIzX4FfjPycAoW/qWjzgb6sjOPDw4JJJvUT/Q== X-Received: by 2002:a05:6a00:4608:b0:736:450c:fa56 with SMTP id d2e1a72fcca58-73bd11a2d89mr2013365b3a.5.1744347863151; Thu, 10 Apr 2025 22:04:23 -0700 (PDT) Received: from [192.168.68.55] ([180.233.125.65]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73bd230f09bsm519649b3a.156.2025.04.10.22.04.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Apr 2025 22:04:21 -0700 (PDT) Message-ID: <44dff493-9d79-4343-ba81-0c262d7a5b4e@redhat.com> Date: Fri, 11 Apr 2025 15:04:16 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drivers/base/memory: Avoid overhead from for_each_present_section_nr() To: David Hildenbrand , Oscar Salvador Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, adityag@linux.ibm.com, donettom@linux.ibm.com, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, akpm@linux-foundation.org, shan.gavin@gmail.com References: <20250410125110.1232329-1-gshan@redhat.com> <9deb3725-8991-43d1-8c3d-56523fabff28@redhat.com> From: Gavin Shan In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JbsAD_Xwwaw1TYCR9rV4hKG7zGMpVCoQxgpnpBgINqE_1744347864 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D92E740004 X-Stat-Signature: upg3fnbexsexwu44hpp5czdymoh33kjt X-HE-Tag: 1744347866-985777 X-HE-Meta: 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 imi+qVbf 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000067, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/11/25 12:25 AM, David Hildenbrand wrote: > On 10.04.25 16:12, Oscar Salvador wrote: >> On Thu, Apr 10, 2025 at 03:55:19PM +0200, Oscar Salvador wrote: >>> All in all, I think we are better, and the code is slightly simpler? >> >> One thing to notice is that maybe we could further improve and leap 'nr' >> by the number of sections_per_block, so in those scenarios where >> a memory-block spans multiple sections this could be faster? > > Essentially, when we created a block we could always start with the next section that starts after the block. > I think it's a good point. Tried a quick test on a ARM64 machine whose memory capacity is 1TB. Leaping 'nr' by 'sections_per_block' improves the performance a bit, even it's not too much. The time taken by memory_dev_init() drops from 110ms to 100ms. For the IBM Power9 machine (64GB memory) I have, there are not too much space to be improved because the time taken by memory_dev_init() is only 10ms. I will post a patch for review after this patch gets merged, if you agree. for_each_present_section_nr(0, nr) { - if (block_id != ULONG_MAX && memory_block_id(nr) == block_id) - continue; - - block_id = memory_block_id(nr); - ret = add_memory_block(block_id, MEM_ONLINE, NULL, NULL); + ret = add_memory_block(memory_block_id(nr), MEM_ONLINE, NULL, NULL); if (ret) { panic("%s() failed to add memory block: %d\n", __func__, ret); } + + /* Align to next block, minus one section */ + nr = ALIGN(nr + 1, sections_per_block) - 1; } Thanks, Gavin