From: Dave Hansen <dave.hansen@intel.com>
To: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: n-horiguchi@ah.jp.nec.com, kirill.shutemov@linux.intel.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, minchan@kernel.org, vbabka@suse.cz,
mgorman@techsingularity.net, mhocko@kernel.org,
khandual@linux.vnet.ibm.com, dnellans@nvidia.com
Subject: Re: [PATCH v5 01/11] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1
Date: Fri, 19 May 2017 09:36:22 -0700 [thread overview]
Message-ID: <ea4597a9-d5a3-4f66-af44-b99f396acf66@intel.com> (raw)
In-Reply-To: <07441274-3C64-4376-8225-39CD052399B4@cs.rutgers.edu>
On 05/19/2017 09:31 AM, Zi Yan wrote:
>> This description lacks a problem statement. What's the problem?
>>
>> _PAGE_PSE is used to distinguish between a truly non-present
>> (_PAGE_PRESENT=0) PMD, and a PMD which is undergoing a THP
>> split and should be treated as present.
>>
>> But _PAGE_SWP_SOFT_DIRTY currently uses the _PAGE_PSE bit,
>> which would cause confusion between one of those PMDs
>> undergoing a THP split, and a soft-dirty PMD.
>>
>> Thus, we need to move the bit.
>>
>> Does that capture it?
> Yes. I will add this in the next version.
OK, thanks for clarifying. You can add my acked-by on this.
But, generally, these bits really scare me. We don't have any nice
programmatic way to find conflicts. I really wish we had some
BUILD_BUG_ON()s or something to express these dependencies.
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next prev parent reply other threads:[~2017-05-19 16:36 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-20 20:47 [PATCH v5 00/11] mm: page migration enhancement for thp Zi Yan
2017-04-20 20:47 ` [PATCH v5 01/11] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1 Zi Yan
2017-05-19 13:07 ` Anshuman Khandual
2017-05-19 15:55 ` Dave Hansen
2017-05-19 16:31 ` Zi Yan
2017-05-19 16:36 ` Dave Hansen [this message]
2017-04-20 20:47 ` [PATCH v5 02/11] mm: mempolicy: add queue_pages_node_check() Zi Yan
2017-04-21 4:04 ` Anshuman Khandual
2017-05-19 13:13 ` Anshuman Khandual
2017-05-19 16:02 ` Mel Gorman
2017-05-19 16:37 ` Zi Yan
2017-05-19 20:28 ` Mel Gorman
2017-05-19 20:48 ` Zi Yan
2017-05-19 21:39 ` Mel Gorman
2017-04-20 20:47 ` [PATCH v5 03/11] mm: thp: introduce separate TTU flag for thp freezing Zi Yan
2017-04-21 4:29 ` Anshuman Khandual
2017-04-20 20:47 ` [PATCH v5 04/11] mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION Zi Yan
2017-04-21 4:36 ` Anshuman Khandual
2017-04-20 20:47 ` [PATCH v5 05/11] mm: thp: enable thp migration in generic path Zi Yan
2017-04-20 20:47 ` [PATCH v5 06/11] mm: thp: check pmd migration entry in common path Zi Yan
2017-04-21 6:17 ` Anshuman Khandual
2017-04-21 15:17 ` Zi Yan
2017-04-20 20:47 ` [PATCH v5 07/11] mm: soft-dirty: keep soft-dirty bits over thp migration Zi Yan
2017-04-20 20:47 ` [PATCH v5 08/11] mm: hwpoison: soft offline supports " Zi Yan
2017-04-21 8:10 ` Anshuman Khandual
2017-04-21 15:55 ` Zi Yan
2017-04-27 4:41 ` Naoya Horiguchi
2017-04-27 16:39 ` Zi Yan
2017-04-20 20:47 ` [PATCH v5 09/11] mm: mempolicy: mbind and migrate_pages support " Zi Yan
2017-04-21 8:22 ` Anshuman Khandual
2017-04-21 16:00 ` Zi Yan
2017-04-20 20:47 ` [PATCH v5 10/11] mm: migrate: move_pages() supports " Zi Yan
2017-04-20 20:47 ` [PATCH v5 11/11] mm: memory_hotplug: memory hotremove " Zi Yan
2017-05-19 13:56 ` Anshuman Khandual
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