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

Pádraig Brady
2015-09-07T09:52:49Z

On 07/09/15 07:46, Naoya Horiguchi wrote:
> On Mon, Sep 07, 2015 at 02:23:44AM +0000, Horiguchi Naoya(堀口 直也) wrote:
>> On Mon, Sep 07, 2015 at 02:29:53AM +0100, Pádraig Brady wrote:
>>> On 20/08/15 09:26, 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@ah.jp.nec.com>
>>>> Acked-by: Joern Engel <joern@logfs.org>
>>>> Acked-by: David Rientjes <rientjes@google.com>
>>>> ---
>>>> v3 -> v4:
>>>> - suspend Acked-by tag because v3->v4 change is not trivial
>>>> - I stated in previous discussion that HugetlbPages line can contain page
>>>> size info, but that's not necessary because we already have KernelPageSize
>>>> info.
>>>> - merged documentation update, where the current documentation doesn't mention
>>>> AnonHugePages, so it's also added.
>>>> ---
>>>> Documentation/filesystems/proc.txt | 7 +++++--
>>>> fs/proc/task_mmu.c | 29 +++++++++++++++++++++++++++++
>>>> 2 files changed, 34 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git v4.2-rc4/Documentation/filesystems/proc.txt v4.2-rc4_patched/Documentation/filesystems/proc.txt
>>>> index 6f7fafde0884..22e40211ef64 100644
>>>> --- v4.2-rc4/Documentation/filesystems/proc.txt
>>>> +++ v4.2-rc4_patched/Documentation/filesystems/proc.txt
>>>> @@ -423,6 +423,8 @@ Private_Clean: 0 kB
>>>> Private_Dirty: 0 kB
>>>> Referenced: 892 kB
>>>> Anonymous: 0 kB
>>>> +AnonHugePages: 0 kB
>>>> +HugetlbPages: 0 kB
>>>> Swap: 0 kB
>>>> KernelPageSize: 4 kB
>>>> MMUPageSize: 4 kB
>>>> @@ -440,8 +442,9 @@ indicates the amount of memory currently marked as referenced or accessed.
>>>> "Anonymous" shows the amount of memory that does not belong to any file. Even
>>>> a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
>>>> and a page is modified, the file page is replaced by a private anonymous copy.
>>>> -"Swap" shows how much would-be-anonymous memory is also used, but out on
>>>> -swap.
>>>> +"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
>>>> +"HugetlbPages" shows the ammount of memory backed by hugetlbfs page.
>>>> +"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
>>>
>>> There is no distinction between "private" and "shared" in this "huge page" accounting right?
>>
>> Right for current version. And I think that private/shared distinction
>> gives some help.
>>
>>> Would it be possible to account for the huge pages in the {Private,Shared}_{Clean,Dirty} fields?
>>> Or otherwise split the huge page accounting into shared/private?
>
> Sorry, I didn't catch you properly.
> I think that accounting for hugetlb pages should be done only with HugetlbPages
> or any other new field for hugetlb, in order not to break the behavior of existing
> fields.

On a more general note I'd be inclined to just account
for hugetlb pages in Rss and {Private,Shared}_Dirty
and fix any tools that double count.

> So splitting HugetlbPages into shared/private looks good to me.

Yes this is the most compatible solution,
and will allow one to accurately determine
how much core mem a process is using.

thanks!
Pádraig.