Re: [rfc 2/2] smaps: Show zone device memory used

[Balbir Singh <bsingharora@gmail.com>]

On Wed, 18 Oct 2017 12:40:43 +0530
Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:

> On 10/18/2017 12:01 PM, Balbir Singh wrote:
> > With HMM, we can have either public or private zone
> > device pages. With private zone device pages, they should
> > show up as swapped entities. For public zone device pages  
> 
> Might be missing something here but why they should show up
> as swapped entities ? Could you please elaborate.
>

For migrated entries, my use case is to

1. malloc()/mmap() memory
2. call migrate_vma()
3. Look at smaps

It's probably not clear in the changelog.

> > the smaps output can be confusing and incomplete.
> > 
> > This patch adds a new attribute to just smaps to show
> > device memory usage.  
> 
> If we are any way adding a new entry here then why not one
> more for private device memory pages as well. Just being
> curious.
> 

Well, how do you define visibility of device private memory?
Device private is either seen as swapped out or when migrated
back is visible as a part of the mm. Am I missing anything?

> > 
> > Signed-off-by: Balbir Singh <bsingharora@gmail.com>
> > ---
> >  fs/proc/task_mmu.c | 17 +++++++++++++++--
> >  1 file changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 9f1e2b2b5f5a..b7f32f42ee93 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -451,6 +451,7 @@ struct mem_size_stats {
> >  	unsigned long shared_hugetlb;
> >  	unsigned long private_hugetlb;
> >  	unsigned long first_vma_start;
> > +	unsigned long device_memory;
> >  	u64 pss;
> >  	u64 pss_locked;
> >  	u64 swap_pss;
> > @@ -463,12 +464,22 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
> >  	int i, nr = compound ? 1 << compound_order(page) : 1;
> >  	unsigned long size = nr * PAGE_SIZE;
> >  
> > +	/*
> > +	 * We don't want to process public zone device pages further
> > +	 * than just showing how much device memory we have
> > +	 */
> > +	if (is_zone_device_page(page)) {  
> 
> Should not this contain both public and private device pages.
> 

This page is received from _vm_normal_page(.., true), I don't
think device private pages show up here.

> > +		mss->device_memory += size;
> > +		return;
> > +	}
> > +
> >  	if (PageAnon(page)) {
> >  		mss->anonymous += size;
> >  		if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
> >  			mss->lazyfree += size;
> >  	}
> >  
> > +  
> 
> Stray new line.
> 

I can remove it

> >  	mss->resident += size;
> >  	/* Accumulate the size in pages that have been accessed. */
> >  	if (young || page_is_young(page) || PageReferenced(page))
> > @@ -833,7 +844,8 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
> >  			   "Private_Hugetlb: %7lu kB\n"
> >  			   "Swap:           %8lu kB\n"
> >  			   "SwapPss:        %8lu kB\n"
> > -			   "Locked:         %8lu kB\n",
> > +			   "Locked:         %8lu kB\n"  
> 
> Stray changed line.

?? The line has changed


Thanks for the review!

Balbir Singh.

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