From: Dave Hansen <dave.hansen@intel.com>
To: Michal Hocko <mhocko@kernel.org>, Fan Du <fan.du@intel.com>
Cc: akpm@linux-foundation.org, hch@lst.de, dan.j.williams@intel.com,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org
Subject: Re: [PATCH 2/2] Add /proc/PID/{smaps, numa_maps} support for DAX
Date: Wed, 25 Oct 2017 10:14:34 -0700 [thread overview]
Message-ID: <1f673f36-74b0-3321-32a4-a8031d5f268a@intel.com> (raw)
In-Reply-To: <20171025093045.s3rpcuovld22bhqu@dhcp22.suse.cz>
On 10/25/2017 02:30 AM, Michal Hocko wrote:
>>
>> 7f6c17800000-7f6c17e00000 rw-s 00000000 00:06 20559 /dev/dax12.0
>> Size: 6144 kB
>> .
>> .
>> .
>> Ptes@2MB: 6144 kB
> This says how but it doesn't tell why and who is going to use the
> information and what for.
The original motivation was for DAX. They have parallel large page
infrastructure separate from hugetlbfs and THP. Their constraints about
when they can use large pages differ from the normal mm cases, so it is
hard to tell when large pages are in use. For instance, the file on
*disk* has to be 2MB contiguous and aligned to map with 2MB pages even
if the mmap() address is >2MB and 2MB-aligned.
But, in general, this seems like the thing that we probably should have
done in the first place for THP. It's a lot more generic and does not
require someone reading the file to know what the particular
architecture's page sizes are.
next prev parent reply other threads:[~2017-10-25 17:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-25 0:27 [PATCHv3 1/2] proc: mm: export PTE sizes directly in smaps Fan Du
2017-10-25 0:27 ` [PATCH 2/2] Add /proc/PID/{smaps, numa_maps} support for DAX Fan Du
2017-10-25 9:30 ` Michal Hocko
2017-10-25 17:14 ` Dave Hansen [this message]
2017-10-26 14:16 ` Michal Hocko
2017-10-26 14:24 ` Dave Hansen
2017-10-26 14:31 ` Michal Hocko
2017-10-26 14:51 ` Dave Hansen
2017-10-26 15:07 ` Michal Hocko
2017-10-26 15:56 ` Dan Williams
2017-10-27 4:00 ` Du, Fan
2017-10-27 10:31 ` Dan Williams
2017-10-28 2:07 ` kbuild test robot
2017-10-25 9:28 ` [PATCHv3 1/2] proc: mm: export PTE sizes directly in smaps Michal Hocko
2017-10-26 1:41 ` Du, Fan
2017-10-26 5:13 ` [PATCH v4] Add /proc/PID/smaps support for DAX Fan Du
2017-10-26 9:16 ` Dan Williams
2017-10-27 2:49 ` Du, Fan
2017-10-26 14:03 ` Dave Hansen
2017-10-27 2:47 ` Du, Fan
2017-10-27 8:07 ` Michal Hocko
2017-10-27 8:24 ` Du, Fan
2017-10-27 8:42 ` Michal Hocko
2017-10-27 9:03 ` Du, Fan
2017-10-27 9:09 ` Michal Hocko
2017-10-27 9:17 ` Du, Fan
2017-10-27 9:26 ` Michal Hocko
2017-10-27 9:34 ` Du, Fan
2017-10-26 14:19 ` [PATCHv3 1/2] proc: mm: export PTE sizes directly in smaps Michal Hocko
2017-10-26 14:25 ` Dave Hansen
2017-10-29 14:19 ` [lkp-robot] [proc] eb948c71f7: WARNING:at_mm/hugetlb.c:#hugetlb_add_hstate kernel test robot
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