From: Wei Yang <richard.weiyang@gmail.com>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Wei Yang <richard.weiyang@gmail.com>,
linux-mm@kvack.org, akpm@linux-foundation.org
Subject: Re: [PATCH 1/2] mm, pageblock: make sure pageblock won't exceed mem_sectioin
Date: Wed, 5 Dec 2018 22:31:21 +0000 [thread overview]
Message-ID: <20181205223121.p6ecogd7itotiosn@master> (raw)
In-Reply-To: <20181205153733.GB23260@techsingularity.net>
On Wed, Dec 05, 2018 at 03:37:33PM +0000, Mel Gorman wrote:
>On Wed, Dec 05, 2018 at 12:08:20PM +0000, Wei Yang wrote:
>> On Wed, Dec 05, 2018 at 11:15:13AM +0000, Mel Gorman wrote:
>> >On Wed, Dec 05, 2018 at 05:19:04PM +0800, Wei Yang wrote:
>> >> When SPARSEMEM is used, there is an indication that pageblock is not
>> >> allowed to exceed one mem_section. Current code doesn't have this
>> >> constrain explicitly.
>> >>
>> >> This patch adds this to make sure it won't.
>> >>
>> >> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> >
>> >Is this even possible? This would imply that the section size is smaller
>> >than max order which would be quite a crazy selection for a sparesemem
>> >section size. A lot of assumptions on the validity of PFNs within a
>> >max-order boundary would be broken with such a section size. I'd be
>> >surprised if such a setup could even boot, let alone run.
>>
>> pageblock_order has two definitions.
>>
>> #define pageblock_order HUGETLB_PAGE_ORDER
>>
>> #define pageblock_order (MAX_ORDER-1)
>>
>> If CONFIG_HUGETLB_PAGE is not enabled, pageblock_order is related to
>> MAX_ORDER, which ensures it is smaller than section size.
>>
>> If CONFIG_HUGETLB_PAGE is enabled, pageblock_order is not related to
>> MAX_ORDER. I don't see HUGETLB_PAGE_ORDER is ensured to be less than
>> section size. Maybe I missed it?
>>
>
>HUGETLB_PAGE_ORDER is less than MAX_ORDER on the basis that normal huge
>pages (not gigantic) pages are served from the buddy allocator which is
>limited by MAX_ORDER.
>
Maybe I am lost here, I got one possible definition on x86.
#define pageblock_order HUGETLB_PAGE_ORDER
#define HUGETLB_PAGE_ORDER (HPAGE_SHIFT - PAGE_SHIFT)
#define HPAGE_SHIFT PMD_SHIFT
#define PMD_SHIFT PUD_SHIFT
#define PUD_SHIFT 30
This leads to pageblock_order = (30 - 12) = 18 > MAX_ORDER ?
What you mentioned sounds reasonable. A huge page should be less than
MAX_ORDER, otherwise page allocator couldn't handle it. But I don't see
the connection between MAX_ORDER and HUGETLB_PAGE_ORDER. Do we need to
add a check on this? Or it already has similar contrain in code, but I
missed it?
>--
>Mel Gorman
>SUSE Labs
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2018-12-05 22:31 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-05 9:19 Wei Yang
2018-12-05 9:19 ` [PATCH 2/2] mm, page_alloc: cleanup usemap_size() when SPARSEMEM is not set Wei Yang
2018-12-07 9:58 ` Wei Yang
2018-12-05 11:15 ` [PATCH 1/2] mm, pageblock: make sure pageblock won't exceed mem_sectioin Mel Gorman
2018-12-05 12:08 ` Wei Yang
2018-12-05 15:37 ` Mel Gorman
2018-12-05 22:31 ` Wei Yang [this message]
2018-12-06 9:00 ` David Hildenbrand
2018-12-06 9:21 ` Wei Yang
2018-12-06 9:26 ` David Hildenbrand
2018-12-06 9:42 ` Wei Yang
2018-12-08 1:42 ` kbuild test robot
2018-12-09 12:03 ` Wei Yang
2018-12-13 2:26 ` Rong Chen
2018-12-13 3:08 ` Wei Yang
2018-12-13 5:02 ` Rong Chen
2018-12-13 7:28 ` Wei Yang
2018-12-09 13:58 ` kbuild test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181205223121.p6ecogd7itotiosn@master \
--to=richard.weiyang@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox