From: Ryan Roberts <ryan.roberts@arm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>, ran xiaokai <ranxiaokai627@163.com>,
akpm@linux-foundation.org, vbabka@suse.cz,
svetly.todorov@memverge.com, ran.xiaokai@zte.com.cn,
baohua@kernel.org, peterx@redhat.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 2/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages
Date: Wed, 26 Jun 2024 16:18:24 +0100 [thread overview]
Message-ID: <5a31d145-19cd-4a35-9211-dc5091069596@arm.com> (raw)
In-Reply-To: <Znwwrnk77J0xfNxu@casper.infradead.org>
On 26/06/2024 16:15, Matthew Wilcox wrote:
> On Wed, Jun 26, 2024 at 12:07:04PM +0100, Ryan Roberts wrote:
>> On 26/06/2024 04:06, Zi Yan wrote:
>>> On Tue Jun 25, 2024 at 10:49 PM EDT, ran xiaokai wrote:
>>>> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
>>>>
>>>> KPF_COMPOUND_HEAD and KPF_COMPOUND_TAIL are set on "common" compound
>>>> pages, which means of any order, but KPF_THP should only be set
>>>> when the folio is a 2M pmd mappable THP.
>>
>> Why should KPF_THP only be set on 2M THP? What problem does it cause as it is
>> currently configured?
>>
>> I would argue that mTHP is still THP so should still have the flag. And since
>> these smaller mTHP sizes are disabled by default, only mTHP-aware user space
>> will be enabling them, so I'll naively state that it should not cause compat
>> issues as is.
>>
>> Also, the script at tools/mm/thpmaps relies on KPF_THP being set for all mTHP
>> sizes to function correctly. So that would need to be reworked if making this
>> change.
>
> I told you you'd run into trouble calling them "mTHP" ...
"There are two hard things in computer science; naming, cache invalidation and
off-by-one errors"
next prev parent reply other threads:[~2024-06-26 15:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-26 2:49 [PATCH 0/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages ran xiaokai
2024-06-26 2:49 ` [PATCH 1/2] mm: Constify folio_order()/folio_test_pmd_mappable() ran xiaokai
2024-06-26 3:09 ` Zi Yan
2024-06-26 4:30 ` ran xiaokai
2024-06-26 11:19 ` Zi Yan
2024-06-26 2:49 ` [PATCH 2/2] kpageflags: fix wrong KPF_THP on non-pmd-mappable compound pages ran xiaokai
2024-06-26 3:06 ` Zi Yan
2024-06-26 4:32 ` ran xiaokai
2024-06-26 11:07 ` Ryan Roberts
2024-06-26 14:40 ` Zi Yan
2024-06-26 14:42 ` Ryan Roberts
2024-06-27 1:54 ` Lance Yang
2024-06-27 4:10 ` Barry Song
2024-06-27 8:39 ` Ryan Roberts
2024-06-27 9:16 ` Barry Song
2024-06-27 9:27 ` Ryan Roberts
2024-06-27 12:46 ` ran xiaokai
2024-06-26 15:15 ` Matthew Wilcox
2024-06-26 15:18 ` Ryan Roberts [this message]
2024-06-27 2:07 ` Lance Yang
2024-06-26 15:55 ` kernel test robot
2024-06-26 16:21 ` kernel test robot
2024-06-27 12:38 ` ran xiaokai
2024-06-27 13:03 ` Zi Yan
2024-06-27 13:16 ` ran xiaokai
2024-06-27 13:54 ` David Hildenbrand
2024-06-28 3:01 ` ran xiaokai
2024-07-03 9:20 ` ran xiaokai
2024-07-03 10:11 ` David Hildenbrand
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