From: Matthew Wilcox <willy@infradead.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
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 04:28:33 +0100 [thread overview]
Message-ID: <YOJ8YR8wWkiHsRTp@casper.infradead.org> (raw)
In-Reply-To: <45c1feaa-4bab-91d1-6962-81549d2b6d00@arm.com>
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?
next prev parent reply other threads:[~2021-07-05 3:28 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 [this message]
2021-07-05 3:39 ` Anshuman Khandual
2021-07-05 11:30 ` Matthew Wilcox
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