Messages in this thread | | | Date | Mon, 30 Jan 2012 10:49:39 -0800 (PST) | From | Hugh Dickins <> | Subject | Re: [Help] : RSS/PSS showing 0 during smaps for Xorg |
| |
On Mon, 30 Jan 2012, PINTU KUMAR wrote: > > >If these are ordinary pages with struct pages, then you could probably > >use a loop of vm_insert_page()s to insert them at mmap time, or a fault > >routine to insert them on fault. But as I said, I don't know if this > >memory is part of the ordinary page pool or not. > > You suggestion about using vm_insert_page() instead of remap_pfn_range worked for me and I got the Rss/Pss information for my driver.
Oh, I'm glad that happened to work for you.
> But still there is one problem related to page fault. > If I remove remap_pfn_range then I get a page fault in the beginning. > I tried to use the same vm_insert_page() during page_fault_handler for each vmf->virtual_address but it did not work. > So for time being I remove the page fault handler from my vm_operations. > But with these my menu screen(LCD screen) is not behaving properly (I get colorful lines on my LCD). > So I need to handle the page fault properly. > > But I am not sure what is that I need to do inside page fault handler. Do you have any example or references or suggestions?
Sounds like you're not using vm_insert_page() properly: I would not expect you to get a page fault there once you've set up the area with a loop of vm_insert_page()s.
Check the comments above it in mm/memory.c ("Your vma protection will have to be set up correctly" might be relevant).
Compare how you're using it with other users of vm_insert_page() in the kernel tree. Sorry, I don't have time to do your debugging.
> > >Really, the question has to be, why do you need to see non-0s there? > I want Rss/Pss value to account for how much video memory is used by the driver for the menu-screen,Xorg processes.
So, userspace does an mmap for a large-enough window, but only some part of that is filled by the driver (whether by remap_pfn_range or vm_insert_pages), and you'd like to communicate back how much via the Rss, instead of adding some ioctl or sysfs interface to the driver? Fair enough.
I expect userspace could also work it out by touching pages of the area until it gets a SIGBUS, but that might be too dirty a way of finding out.
Hmm, SIGBUS: maybe that's related to the faults that are puzzling you: perhaps you're mapping less than you need to.
Hugh | |