On Thu, Nov 7, 2019 at 11:00 AM Won-Kyo Choe <[email protected]> wrote: > > On Thu, Nov 07, 2019 at 07:54:21AM -0800, Dan Williams wrote: > > On Thu, Nov 7, 2019 at 7:30 AM Won-Kyo Choe <[email protected]> wrote: > > > > > > Hi, there. I'm using Opatne DC memory to use it a volatile memory. > > > Recently, > > > I found that if sizeof(struct page) is above 64 bytes (e.g. 128 byes), > > > `device_dax` cannot be initialized when system boots. I am aware that > > > for some reason there is a function, `__mm_zero_struct_page`, which limits > > > the size of struct page when it exceeds 80 bytes. However, due to the > > > research purpose, I do not use that constraint and I'm quite certain > > > that using different page size is usable in main memory. So, I'm > > > wondering why this is not possible in persistent memory and which > > > patches are related to this problem. > > > > > > I will attach the system log for clarification. The test is run in > > > linux-5.3.9 and linuxt-5.3-rc5 > > > > How did you manage to build the kernel with a 128byte struct page > > size? This build assert in drivers/nvdimm/pfn_devs.c > > > > BUILD_BUG_ON(sizeof(struct page) > MAX_STRUCT_PAGE_SIZE); > > > > ...will start to trigger in v5.4 to explicitly prevent this going > > forward. See commit e96f0bf2ec92 "libnvdimm/pfn_dev: Add a build check > > to make sure we notice when struct page size change" for more details. > > > Thanks for the related commit. The kernel that I am using (5.3.9 / 5.3-rc5) > does > not have the assert so that I was able to build it by little bit modifying > lines > in include/linux/mm.h > > BUILD_BUG_ON(sizeof(struct page) > 80); > ... > > , which is quite similar with the assert you referred. > > > In general 64-bytes per page is already expensive 128 bytes is a > > gigantic struct page. > Yes. I am aware that issue. I just wanted to add hot-page tracking > feature by inserting some data structure collecting it inside struct page > but the size is matter. I should find another way to get that stat :)
For hot page tracking you may want to look at some of the discussion around Memory Hierarchy support: https://lore.kernel.org/linux-mm/[email protected]/ _______________________________________________ Linux-nvdimm mailing list -- [email protected] To unsubscribe send an email to [email protected]
