On 7/27/22 09:44, Kassey Li wrote: > > > On 7/26/2022 10:03 PM, Vlastimil Babka (SUSE) wrote: >> On 7/25/22 10:39, Kassey Li wrote: >>> hi, Matthew: >>> sorry for the delay, I just started to learn how to upstream patch, and >>> setup my Thunderbird with plain text only. >>> you are right, two users will cause problem here. >>> the uses case is dump CMA area to understand the page usage in a given >>> cma pool. 2nd, dump whole memory page owner is very time cost, mostly our >>> android device has 8G memory now. >>> I will research and check again, if you have more idea on this , please >>> kindly to share. >> >> You could try employing lseek() to specify the start pfn, and as for end >> pfn, the process can just stop reading and close when it has seen enough? > > lseek is a good idea. > read_page_owner start with below > pfn = min_low_pfn + *ppos; > so we need to export the min_low_pfn to user then decide the ppos to seek. > (my_cma.base_pfn - min_low_pfn) is the ppos we want to set. Hm could we just pfn = *ppos and then anything below min_low_pfn is skipped internally? So we don't need to teach userspace min_low_pfn. > is there concern to export min_low_pfn ? > or use a mutex lock for my previous debugfs version patch ? > >> >>> BR >>> Kassey >>> >>> On 7/22/2022 11:38 PM, Matthew Wilcox wrote: >>>> On Fri, Jul 22, 2022 at 11:08:10PM +0800, Kassey Li wrote: >>>>> by default, page_owner iterates all page from min_low_pfn to >>>>> max_pfn, this cost too much time if we want an alternative pfn range. >>>>> >>>>> with this patch it allows user to set pfn range to dump the page_onwer. >>>> >>>> This is a really bad UI. If two users try to do different ranges at the >>>> same time, it'll go wrong. What use cases are you actually trying to >>>> solve? >>> >>
