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Wed, 06 Aug 2025 07:31:04 -0700 (PDT) Date: Wed, 6 Aug 2025 14:31:03 +0000 From: Wei Yang To: Sumanth Korikkar Cc: Wei Yang , Andrew Morton , linux-mm , LKML , David Hildenbrand , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390 Subject: Re: [PATCH v2] mm: fix accounting of memmap pages for early sections Message-ID: <20250806143103.xkdz4sinbhcq4vyd@master> Reply-To: Wei Yang References: <20250804151328.2326642-1-sumanthk@linux.ibm.com> <20250806090320.wdt4zsfiambtgkvy@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Queue-Id: D0B011A0018 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: e1rumg68119x8upu1jgtfhi3cjknhtaw X-HE-Tag: 1754490666-691739 X-HE-Meta: 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 EZYHUvjk 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Wed, Aug 06, 2025 at 02:46:43PM +0200, Sumanth Korikkar wrote: >> The change here is reasonable. While maybe we still miss the counting at some >> other points. >> >> For example: >> >> a. >> >> sparse_init_nid() >> __populate_section_memmap() >> >> If !CONFIG_SPARSEMEM_VMEMMAP, and sparse_buffer_alloc() return NULL, it >> allocate extra memory from bootmem, which looks not counted. > >Currently, the accounting is done upfront in sparse_buffer_init(), where >memmap_boot_pages_add() is called for !CONFIG_SPARSEMEM_VMEMMAP. > >The function sparse_buffer_alloc() can return NULL in two scenarios: > >* During sparse_buffer_init(), if memmap_alloc() fails, sparsemap_buf will be NULL. >* Inside sparse_buffer_alloc(), if ptr + size exceeds sparsemap_buf_end, > then ptr is set to NULL. > >Considering this, perhaps memmap_boot_pages_add() could be moved into >__populate_section_memmap(), with the accounting done only if the >operation is successful. What do you think? > Looks reasonable to me. >> section_activate() >> populate_section_memmap() >> >> If !CONFIG_SPARSEMEM_VMEMMAP, it just call kvmalloc_node(), which looks not >> counted. > >Sounds right. This means nr_memmap_pages adjustment is needed for >!CONFIG_SPARSEMEM_VMEMMAP here. I will recheck this. > >Thank you -- Wei Yang Help you, Help me