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imf12.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf12.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744595537; a=rsa-sha256; cv=none; b=I3YzlPp8jmMx455tXeXFI9rMNdzZjI81+x6ja0Birk7+PQlZo1QRDd40dG5RFlWrTFzhLb bH0Nnyp9NslZ9UtTuJ9iMtVWSqpy6B2NkWB5/rushU4ttrnfXqx7Y8Sn20lwu/mxMOpUh6 PYV25N+P2aCR8HQZ1m89YXYvkg4zqAo= X-AuditID: a67dfc5b-669ff7000002311f-a5-67fc6a4caab5 Date: Mon, 14 Apr 2025 10:52:07 +0900 From: Byungchul Park To: willy@infradead.org, ilias.apalodimas@linaro.org, almasrymina@google.com Cc: kernel_team@skhynix.com, 42.hyeyoo@gmail.com, linux-mm@kvack.org, hawk@kernel.org, netdev@vger.kernel.org Subject: Re: [RFC] shrinking struct page (part of page pool) Message-ID: <20250414015207.GA50437@system.software.com> References: <20250414013627.GA9161@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250414013627.GA9161@system.software.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrNLMWRmVeSWpSXmKPExsXC9ZZnoa5P1p90gxdTdSwm9hhYrP5RYbGn fTuzRW/Lb2aLe2v+s1ocWyBm8fvHHDYHdo+ds+6yeyzYVOqxeYWWx6ZVnWwemz5NYve4c20P m8fnTXIB7FFcNimpOZllqUX6dglcGW/uXWQvOM9f8X3CbcYGxm6eLkZODgkBE4kXv78yw9h9 jzsYQWwWAVWJs2+PsYLYbALqEjdu/ASrERHwk2idcpwFxGYWyJdounIMrF5YwEZi+4+5YPW8 AhYSk26uBasREjCXWLL9DwtEXFDi5MwnUL1aEjf+vWTqYuQAsqUllv/jAAlzArVum7McrERU QFniwLbjQCVcQKetYZN4e+8cI8SdkhIHV9xgmcAoMAvJ2FlIxs5CGLuAkXkVo1BmXlluYmaO iV5GZV5mhV5yfu4mRmCQL6v9E72D8dOF4EOMAhyMSjy8CYd/pwuxJpYVV+YeYpTgYFYS4eVy /pUuxJuSWFmVWpQfX1Sak1p8iFGag0VJnNfoW3mKkEB6YklqdmpqQWoRTJaJg1OqgXGpd8U2 J514WTmrTZ7ZXx8caTxT/1Gx7dJW5ii/J4lCZx+pHDnwkTNgV5XaYpu4x52OP8Kq3n+aZpnJ fqTYoZn/uMOSW3f7k/P1Jrq9sYzdrfRtF4vPnkvXshI2LoiwWHTl1eLmSbar2H+IC3p4/ef7 rxl5eI/RpWq27QFr+xJVXTrNPvR2nlJiKc5INNRiLipOBADI4TmGbgIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrELMWRmVeSWpSXmKPExsXC5WfdrOuT9Sfd4PAHBYuJPQYWq39UWOxp 385s0dvym9ni8NyTrBb31vxntTi2QMzi9485bA4cHjtn3WX3WLCp1GPzCi2PTas62Tw2fZrE 7nHn2h42j8UvPjB5fN4kF8ARxWWTkpqTWZZapG+XwJXx5t5F9oLz/BXfJ9xmbGDs5uli5OSQ EDCR6HvcwQhiswioSpx9e4wVxGYTUJe4ceMnM4gtIuAn0TrlOAuIzSyQL9F05RhYvbCAjcT2 H3PB6nkFLCQm3VwLViMkYC6xZPsfFoi4oMTJmU+gerUkbvx7ydTFyAFkS0ss/8cBEuYEat02 ZzlYiaiAssSBbceZJjDyzkLSPQtJ9yyE7gWMzKsYRTLzynITM3NM9YqzMyrzMiv0kvNzNzEC Q3ZZ7Z+JOxi/XHY/xCjAwajEw5tw+He6EGtiWXFl7iFGCQ5mJRFeLudf6UK8KYmVValF+fFF pTmpxYcYpTlYlMR5vcJTE4QE0hNLUrNTUwtSi2CyTBycUg2MHsX2uh3Tgt4ds5hcsk3H3neW 3Q59+Vlrmz4y2iWuf5J2+M+M+ivX1dQqjoV8+bDbrnHKsTKP5COK4WU8rEtiSlXuM2dy99d0 PNgdxt24j6Gh5kPpRqUlYgt7n2Zs+7hEvO3dtPzwAzm5biwzNn6/vbn9dOsliWs/av1mKbUw bN22e56mbsUrJZbijERDLeai4kQAJw1ECFUCAAA= X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6FB6F40002 X-Stat-Signature: se9dsyqrhj1o4b98tkkadisgso31wz6z X-HE-Tag: 1744595536-887735 X-HE-Meta: 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 uXqIY/Vm EJCUtbPvk5e+SBkdDol/j1FQMO117J/0WmQoztquSfL5b4Ia1uRjmWYTDINgXiMeWxOnIdcKRXkqfd+yb0Y55W5L9CA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000431, 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 Mon, Apr 14, 2025 at 10:36:27AM +0900, Byungchul Park wrote: > Hi guys, +cc hawk@kernel.org +cc netdev@vger.kernel.org Byungchul > I'm looking at network's page pool code to help 'shrinking struct page' > project by Matthew Wilcox. See the following link: > > https://kernelnewbies.org/MatthewWilcox/Memdescs/Path > > My first goal is to remove fields for page pool from struct page like: > > struct { /* page_pool used by netstack */ > /** > * @pp_magic: magic value to avoid recycling non > * page_pool allocated pages. > */ > unsigned long pp_magic; > struct page_pool *pp; > unsigned long _pp_mapping_pad; > unsigned long dma_addr; > atomic_long_t pp_ref_count; > }; > > Fortunately, many prerequisite works have been done by Mina but I guess > he or she has done it for other purpose than 'shrinking struct page'. > > I'd like to just finalize the work so that the fields above can be > removed from struct page. However, I need to resolve a curiousity > before starting. > > Network guys already introduced a sperate strcut, struct net_iov, > to overlay the interesting fields. However, another separate struct > for system memory might be also needed e.g. struct bump so that > struct net_iov and struct bump can be overlayed depending on the > source: > > struct bump { > unsigned long _page_flags; > unsigned long bump_magic; > struct page_pool *bump_pp; > unsigned long _pp_mapping_pad; > unsigned long dma_addr; > atomic_long_t bump_ref_count; > unsigned int _page_type; > atomic_t _refcount; > }; > > To netwrok guys, any thoughts on it? > To Willy, do I understand correctly your direction? > > Plus, it's a quite another issue but I'm curious, that is, what do you > guys think about moving the bump allocator(= page pool) code from > network to mm? I'd like to start on the work once gathering opinion > from both Willy and network guys. > > Byungchul