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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F3612A0002 X-Stat-Signature: e8xwuk3ta7tiudkmzdjbotgcswxp979x X-Rspam-User: X-HE-Tag: 1677729061-513392 X-HE-Meta: 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 VvENOksw dmwxEfmAACHzijsBIXD0omkNCKIhBOfIb8tT4vEc7+QrFBJosVrY/tnvhoZMlcIelHDG67fZIRGN773VnOSH62QIEBHeWNHNtLgSQvSacOFOJXPAtXMZEM02ZFO4FM3TrSRylDh6bxrDGRFapO22bahdPxplztWqv/xb3hI+0aHaN82T55rBe9hPzDOiVVAjoHG+kbSqWrad52NwQpMaqarc4oEDUeriKSa3i7IvCmTzG718Wc4WyLIQK+ZVjR6520q38T6JmWMqze3kTT3z3Ymh9pw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.005086, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 21, 2023 at 2:58=E2=80=AFPM Matthew Wilcox wrote: > > On Wed, Feb 22, 2023 at 02:08:28AM +0800, Gao Xiang wrote: > > On 2023/1/27 00:40, Matthew Wilcox wrote: > > > I'd like to do another session on how the struct page dismemberment > > > is going and what remains to be done. Given how widely struct page i= s > > > used, I think there will be interest from more than just MM, so I'd > > > suggest a plenary session. > > > > I'm interested in this topic too, also I'd like to get some idea of the > > future of the page dismemberment timeline so that I can have time to ke= ep > > the pace with it since some embedded use cases like Android are > > memory-sensitive all the time. > > As you all know, I'm absolutely amazing at project management & planning > and can tell you to the day when a feature will be ready ;-) > > My goal for 2023 is to get to a point where we (a) have struct page > reduced to: > > struct page { > unsigned long flags; > struct list_head lru; > struct address_space *mapping; > pgoff_t index; > unsigned long private; > atomic_t _mapcount; > atomic_t _refcount; > unsigned long memcg_data; > #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS > int _last_cpupid; > #endif > }; This looks clean, but it is still 64-bytes. I wonder if we could potentially reduce it down to 56 bytes by removing memcg_data. Something like this might work: 1. On a 64-bit system flags field contains 19 unused bits, we could potentially use the free bits in this field. 2. There are up-to 64K memcg ids. So in case this field contains memcg pointer 16-bit id would be enough to convert to memcg pointer 3. In case memcg_data contains a pointer to a list of memcgs, there could be a separate hash table data structure that contains pointers to memcgs for slabs, or other users. However, I am not sure how that would affect the performance, but it would be very nice to reduce "struct page" by 8-bytes. Pasha