From: Ryan Roberts <ryan.roberts@arm.com>
To: Matthew Wilcox <willy@infradead.org>,
"Huang, Ying" <ying.huang@intel.com>
Cc: Yu Zhao <yuzhao@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Yin Fengwei <fengwei.yin@intel.com>,
David Hildenbrand <david@redhat.com>,
Yang Shi <shy828301@gmail.com>, Zi Yan <ziy@nvidia.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v3 2/3] mm: Implement folio_remove_rmap_range()
Date: Thu, 27 Jul 2023 08:26:44 +0100 [thread overview]
Message-ID: <faf8d723-afb8-ac4e-7861-4004bb78c5a9@arm.com> (raw)
In-Reply-To: <ZMHX+O0wmjuPXdTi@casper.infradead.org>
On 27/07/2023 03:35, Matthew Wilcox wrote:
> On Thu, Jul 27, 2023 at 09:29:24AM +0800, Huang, Ying wrote:
>> Matthew Wilcox <willy@infradead.org> writes:
>>> I think that can make sense. Because we limit to a single page table,
>>> specifying 'nr = 1 << PMD_ORDER' is the same as 'compound = true'.
>>> Just make it folio, page, nr, vma. I'd actually prefer it as (vma,
>>> folio, page, nr), but that isn't the convention we've had in rmap up
>>> until now.
>>
>> IIUC, even if 'nr = 1 << PMD_ORDER', we may remove one PMD 'compound'
>> mapping, or 'nr' PTE mapping. So, we will still need 'compound' (or
>> some better name) as parameter.
>
> Oh, this is removing ... so you're concerned with the case where we've
> split the PMD into PTEs, but all the PTEs are still present in a single
> page table? OK, I don't have a good answer to that. Maybe that torpedoes
> the whole idea; I'll think about it.
This is exactly why I think the approach I've already taken is the correct one;
a 'range' makes no sense when you are dealing with 'compound' pages because you
are accounting the entire folio. So surely its better to reflect that by only
accounting small pages in the range version of the API.
next prev parent reply other threads:[~2023-07-27 7:26 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 11:29 [PATCH v3 0/3] Optimize large folio interaction with deferred split Ryan Roberts
2023-07-20 11:29 ` [PATCH v3 1/3] mm: Allow deferred splitting of arbitrary large anon folios Ryan Roberts
2023-07-20 11:29 ` [PATCH v3 2/3] mm: Implement folio_remove_rmap_range() Ryan Roberts
2023-07-26 5:53 ` Yu Zhao
2023-07-26 6:42 ` Ryan Roberts
2023-07-26 16:44 ` Matthew Wilcox
2023-07-27 1:29 ` Huang, Ying
2023-07-27 2:35 ` Matthew Wilcox
2023-07-27 7:26 ` Ryan Roberts [this message]
2023-07-27 16:38 ` Yu Zhao
2023-07-28 9:00 ` Ryan Roberts
2023-08-01 7:40 ` Yu Zhao
2023-07-20 11:29 ` [PATCH v3 3/3] mm: Batch-zap large anonymous folio PTE mappings Ryan Roberts
2023-07-26 16:19 ` Nathan Chancellor
2023-07-26 16:32 ` Ryan Roberts
2023-07-26 16:35 ` Nathan Chancellor
2023-07-26 19:38 ` Ryan Roberts
2023-07-26 19:50 ` Nathan Chancellor
2023-07-26 21:17 ` Ryan Roberts
2023-07-26 21:23 ` Nathan Chancellor
2023-07-26 21:28 ` Ryan Roberts
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