From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
Vlastimil Babka <vbabka@suse.cz>,
Randy Dunlap <rdunlap@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] mm/thp: Make ALLOC_SPLIT_PTLOCKS dependent on USE_SPLIT_PTE_PTLOCKS
Date: Mon, 5 Jul 2021 09:09:22 +0530 [thread overview]
Message-ID: <67a7c36d-a040-b58a-ab8b-d67ba4341369@arm.com> (raw)
In-Reply-To: <YOJ8YR8wWkiHsRTp@casper.infradead.org>
On 7/5/21 8:58 AM, Matthew Wilcox wrote:
> On Mon, Jul 05, 2021 at 08:57:54AM +0530, Anshuman Khandual wrote:
>>
>> On 7/1/21 6:27 PM, Matthew Wilcox wrote:
>>> On Thu, Jul 01, 2021 at 10:51:27AM +0530, Anshuman Khandual wrote:
>>>>
>>>>
>>>> On 5/20/21 4:47 PM, Matthew Wilcox wrote:
>>>>> On Wed, May 19, 2021 at 01:03:06PM +0530, Anshuman Khandual wrote:
>>>>>> Split ptlocks need not be defined and allocated unless they are being used.
>>>>>> ALLOC_SPLIT_PTLOCKS is inherently dependent on USE_SPLIT_PTE_PTLOCKS. This
>>>>>> just makes it explicit and clear. While here drop the spinlock_t element
>>>>>> from the struct page when USE_SPLIT_PTE_PTLOCKS is not enabled.
>>>>>
>>>>> I didn't spot this email yesterday. I'm not a fan. Isn't struct page
>>>>> already complicated enough without adding another ifdef to it? Surely
>>>>> there's a better way than this.
>>>>
>>>> This discussion thread just got dropped off the radar, sorry about it.
>>>> None of the spinlock_t elements are required unless split ptlocks are
>>>> in use. I understand your concern regarding yet another #ifdef in the
>>>> struct page definition. But this change is simple and minimal. Do you
>>>> have any other particular alternative in mind which I could explore ?
>>>
>>> Do nothing? I don't understand what problem you're trying to solve.
>>
>> Currently there is an element (spinlock_t ptl) in the struct page for page
>> table lock. Although a struct page based spinlock is not even required in
>> case USE_SPLIT_PTE_PTLOCKS evaluates to be false. Is not that something to
>> be fixed here i.e drop the splinlock_t element if not required ?
>
> No? It doesn't actually cause any problems, does it?
>
No but should an unnecessary element in a struct is dropped only if there
is a reported problem ?
next prev parent reply other threads:[~2021-07-05 3:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 7:33 [PATCH V2] mm/thp: Make ALLOC_SPLIT_PTLOCKS dependent on USE_SPLIT_PTE_PTLOCKS Anshuman Khandual
2021-05-20 11:17 ` Matthew Wilcox
2021-07-01 5:21 ` Anshuman Khandual
2021-07-01 12:57 ` Matthew Wilcox
2021-07-05 3:27 ` Anshuman Khandual
2021-07-05 3:28 ` Matthew Wilcox
2021-07-05 3:39 ` Anshuman Khandual [this message]
2021-07-05 11:30 ` Matthew Wilcox
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