Re: [PATCH 2/4] mm, procfs: account for shmem swap in /proc/pid/smaps

[Vlastimil Babka]

On 03/11/2015 01:30 PM, Konstantin Khlebnikov wrote:
> On Thu, Feb 26, 2015 at 4:51 PM, Vlastimil Babka <vbabka@xxxxxxx> wrote:
> > Currently, /proc/pid/smaps will always show "Swap: 0 kB" for shmem-backed
> > mappings, even if the mapped portion does contain pages that were swapped out.
> > This is because unlike private anonymous mappings, shmem does not change pte
> > to swap entry, but pte_none when swapping the page out. In the smaps page
> > walk, such page thus looks like it was never faulted in.
>
> Maybe just add count of swap entries allocated by mapped shmem into
> swap usage of this vma? That's isn't exactly correct for partially
> mapped shmem but this is something weird anyway.

Yeah for next version I want to add a patch optimizing for the 
(hopefully) common cases:

1. SHMEM_I(inode)->swapped is 0 - no need to consult radix tree
2. shmem inode is mapped fully (I hope it's ok to just compare its size 
and mapping size) - just use the value of SHMEM_I(inode)->swapped like 
you suggest



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