On 11/17/2016 01:28 AM, Dave Hansen wrote:
Changes from v1:
* Do one 'Pte' line per pte size instead of mashing on one line
* Use PMD_SIZE for pmds instead of PAGE_SIZE, whoops
* Wrote some Documentation/
--
/proc/$pid/smaps has a number of fields that are intended to imply the
kinds of PTEs used to map memory. "AnonHugePages" obviously tells you
how many PMDs are being used. "MMUPageSize" along with the "Hugetlb"
fields tells you how many PTEs you have for a huge page.
The current mechanisms work fine when we have one or two page sizes.
But, they start to get a bit muddled when we mix page sizes inside
one VMA. For instance, the DAX folks were proposing adding a set of
fields like:
DevicePages:
DeviceHugePages:
DeviceGiganticPages:
DeviceGinormousPages:
to unmuddle things when page sizes get mixed. That's fine, but
it does require userspace know the mapping from our various
arbitrary names to hardware page sizes on each architecture and
kernel configuration. That seems rather suboptimal.
What folks really want is to know how much memory is mapped with
each page size. How about we just do *that*?
Patch attached. Seems harmless enough. Seems to compile on a
bunch of random architectures. Makes smaps look like this:
Private_Hugetlb: 0 kB
Swap: 0 kB
SwapPss: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
Ptes@4kB: 32 kB
Ptes@2MB: 2048 kB
The format I used here should be unlikely to break smaps parsers
unless they're looking for "kB" and now match the 'Ptes@4kB' instead
of the one at the end of the line.
1. I'd like to thank Dan Williams for showing me a mirror as I
complained about the bozo that introduced 'AnonHugePages'.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Hmm, why not, I guess. But are HugeTLBs handled correctly?
@@ -702,11 +707,13 @@ static int smaps_hugetlb_range(pte_t *pt
}
if (page) {
int mapcount = page_mapcount(page);
+ unsigned long hpage_size = huge_page_size(hstate_vma(vma));
+ mss->rss_pud += hpage_size;
This hardcoded pud doesn't look right, doesn't the pmd/pud depend on
hpage_size?
if (mapcount >= 2)
- mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
+ mss->shared_hugetlb += hpage_size;
else
- mss->private_hugetlb += huge_page_size(hstate_vma(vma));
+ mss->private_hugetlb += hpage_size;
}
return 0;
}
--
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