________________________________ >From: Hugh Dickins <hughd@xxxxxxxxxx> >To: PINTU KUMAR <pintu_agarwal@xxxxxxxxx> >Cc: "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>; "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx> >Sent: Tuesday, 24 January 2012 1:01 AM >Subject: Re: [Help] : RSS/PSS showing 0 during smaps for Xorg > >On Mon, 23 Jan 2012, PINTU KUMAR wrote: >> Dear All, >> >> I am facing one problem for one of my kernel module for our linux mobile with kernel2.6.36. >> >> When I do cat /proc/<Xorg pid>/smaps | grep -A 11 /dev/ump , to track information for my ump module, >> we always get Rss/Pss as 0 kB as shown below: >> cat /proc/1731/smaps | grep -A 11 /dev/ump >> 414db000-415ff000 rw-s 00015000 00:12 6803 /dev/ump >> Size: 1168 kB >> Rss: 0 kB >> Pss: 0 kB >> track_rss_value = 0, iswalkcalled = 1, smap_pte_range_called = 1, swap_pte = 0, not_pte_present = 0, not_normal_page = 1 >> isspecial = 0, not_special = 1, isMixedMap = 0, pfnpages_null = 0, pfnoff_flag = 0, not_cow_mapping = 1, normal_page_end = 0 >> >> After tracing down the problem, I found out that during "show_smaps" in fs/proc/task_mmu.c and during call to smaps_pte_range the vm_normal_page() is always returning NULL for our /dev/ump driver. >> (smaps_pte_range() is the place where Rss/Pss information is populated) >> Thus mss->resident (Rss value) is never getting incremented. >> >> To trace the problem I added few flags during show_smaps & vm_normal_page() as shown above. The value of 1 indicates that the condition is executed. >> Thus "normal_page_end" indicates that the "vm_normal_page" has never ended successfully and always returns from >> "!is_cow_mapping()". >> >> So, I wanted to know the main cause for vm_normal_page() always returning NULL page for our ump driver. >> What is that I am missing in my driver ? >> >> Can anyone please let me know what could be the problem in our driver. > >This not evidence of any problem in your driver. > >vm_normal_page() returns NULL because the pages mapped by your driver >are not normal faultable and reclaimable pages, but an area of physical >memory mapped in by remap_pfn_range(), which sets the VM_PFNMAP flag. > >The mm subsystem does not count such pages towards rss (or pss), >hence your 0s. > >Hugh > Dear Mr. Hugh, Thank you very much for your reply. Is there a way to convert our mapped pages to a normal pages. I tried pfn_to_page() but no effect. I mean the page is considered normal only if it is associated with "struct page" right??? Is is possible to convert these pages to a normal struct pages so that we can get the Rss/Pss value?? Also, the VM_PFNMAP is being set for all dirvers during remap_pfn_range and stills shows Rss/Pss for other drivers. Then why it is not shown for our driver? How to avoid remap_pfn_range to not to set VM_PFNMAP for our driver? Please let me know. Thanks, Regards, Pintu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href