Re: [PATCH v5 1/2] mm: hugetlb: proc: add HugetlbPages field to /proc/PID/smaps

[David Rientjes]

On Wed, 9 Sep 2015, Vlastimil Babka wrote:

> On 08/20/2015 10:26 AM, Naoya Horiguchi wrote:
> > Currently /proc/PID/smaps provides no usage info for vma(VM_HUGETLB), which
> > is inconvenient when we want to know per-task or per-vma base hugetlb usage.
> > To solve this, this patch adds a new line for hugetlb usage like below:
> > 
> >    Size:              20480 kB
> >    Rss:                   0 kB
> >    Pss:                   0 kB
> >    Shared_Clean:          0 kB
> >    Shared_Dirty:          0 kB
> >    Private_Clean:         0 kB
> >    Private_Dirty:         0 kB
> >    Referenced:            0 kB
> >    Anonymous:             0 kB
> >    AnonHugePages:         0 kB
> >    HugetlbPages:      18432 kB
> >    Swap:                  0 kB
> >    KernelPageSize:     2048 kB
> >    MMUPageSize:        2048 kB
> >    Locked:                0 kB
> >    VmFlags: rd wr mr mw me de ht
> > 
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> > Acked-by: Joern Engel <joern@xxxxxxxxx>
> > Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> 
> Sorry for coming late to this thread. It's a nice improvement, but I find it
> somewhat illogical that the per-process stats (status) are more detailed than
> the per-mapping stats (smaps) with respect to the size breakdown. I would
> expect it to be the other way around. That would simplify the per-process
> accounting (I realize this has been a hot topic already), and allow those who
> really care to look at smaps.
> 

Smaps shows the pagesize for the hugepage of the vma and the rss, I 
believe you have all the information needed.  Some distributions also 
change smaps to only be readable by the owner or root for security 
reasons.
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