From: Balbir Singh <bsingharora@gmail.com>
To: Michal Hocko <mhocko@suse.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>, linux-mm <linux-mm@kvack.org>
Subject: Re: [rfc 2/2] smaps: Show zone device memory used
Date: Sat, 21 Oct 2017 08:55:59 +1100 [thread overview]
Message-ID: <CAKTCnzkdoC6aVKSkTS95+MyVLHbMaEiUXaAJUXSicmdCZPNCNw@mail.gmail.com> (raw)
In-Reply-To: <20171020130845.m5sodqlqktrcxkks@dhcp22.suse.cz>
On Sat, Oct 21, 2017 at 12:08 AM, Michal Hocko <mhocko@suse.com> wrote:
> On Wed 18-10-17 17:31:23, 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
>> the smaps output can be confusing and incomplete.
>>
>> This patch adds a new attribute to just smaps to show
>> device memory usage.
>
> As this will become user API which we will have to maintain for ever I
> would really like to hear about who is going to use this information and
> what for.
This is something I observed when running some tests with HMM/CDM.
The issue I had was that there was no visibility of what happened to the
pages after the following sequence
1. malloc/mmap pages
2. migrate_vma() to ZONE_DEVICE (hmm/cdm space)
3. look at smaps
If we look at smaps after 1 and the pages are faulted in we can see the
pages for the region, but at point 3, there is absolutely no visibility of
what happened to the pages. I thought smaps is a good way to provide
the visibility as most developers use that interface. It's more to fix the
inconsistency I saw w.r.t visibility and accounting.
Balbir Singh.
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next prev parent reply other threads:[~2017-10-20 21:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-18 6:31 [rfc 1/2] mm/hmm: Allow smaps to see zone device public pages Balbir Singh
2017-10-18 6:31 ` [rfc 2/2] smaps: Show zone device memory used Balbir Singh
2017-10-18 7:10 ` Anshuman Khandual
2017-10-18 19:48 ` Balbir Singh
2017-10-19 17:02 ` Jerome Glisse
2017-10-21 1:23 ` Balbir Singh
2017-10-20 13:08 ` Michal Hocko
2017-10-20 21:55 ` Balbir Singh [this message]
2017-10-23 8:49 ` Michal Hocko
2017-10-23 9:32 ` Balbir Singh
2017-10-23 9:36 ` Michal Hocko
2017-10-23 9:37 ` Balbir Singh
2017-10-18 6:56 ` [rfc 1/2] mm/hmm: Allow smaps to see zone device public pages Anshuman Khandual
2017-10-18 19:36 ` Balbir Singh
2017-10-20 13:11 ` Michal Hocko
2017-10-20 21:52 ` Balbir Singh
2017-10-23 8:52 ` Michal Hocko
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