From: Ryan Roberts <ryan.roberts@arm.com>
To: Matthew Wilcox <willy@infradead.org>, Yu Zhao <yuzhao@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Yin Fengwei <fengwei.yin@intel.com>,
David Hildenbrand <david@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Yang Shi <shy828301@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 3/5] mm: Default implementation of arch_wants_pte_order()
Date: Fri, 7 Jul 2023 11:00:37 +0100 [thread overview]
Message-ID: <3500d482-f319-4def-e40d-6d0ae2ada85b@arm.com> (raw)
In-Reply-To: <ZKcW/Zij1HZB0tmf@casper.infradead.org>
On 06/07/2023 20:33, Matthew Wilcox wrote:
> On Tue, Jul 04, 2023 at 08:07:19PM -0600, Yu Zhao wrote:
>>> - On arm64 when the process has marked the VMA for THP (or when
>>> transparent_hugepage=always) but the VMA does not meet the requirements for a
>>> PMD-sized mapping (or we failed to allocate, ...) then I'd like to map using
>>> contpte. For 4K base pages this is 64K (order-4), for 16K this is 2M (order-7)
>>> and for 64K this is 2M (order-5). The 64K base page case is very important since
>>> the PMD size for that base page is 512MB which is almost impossible to allocate
>>> in practice.
>>
>> Which case (server or client) are you focusing on here? For our client
>> devices, I can confidently say that 64KB has to be after 16KB, if it
>> happens at all. For servers in general, I don't know of any major
>> memory-intensive workloads that are not THP-aware, i.e., I don't think
>> "VMA does not meet the requirements" is a concern.
>
> It sounds like you've done some measurements, and I'd like to understand
> those a bit better. There are a number of factors involved:
I'm not sure if that's a question to me or Yu? I haven't personally done any
measurements for the 64K base page case. But Arm has a partner that is pushing
for this. I'm hoping to see some test results from them posted publicly in the
coming weeks. See [1] for more explanation on the rationale.
[1]
https://lore.kernel.org/linux-mm/4d4c45a2-0037-71de-b182-f516fee07e67@arm.com/T/#m8a7c4b71f94224ec3fe6d0a407f48d74c789ba4f
>
> - A larger page size shrinks the length of the LRU list, so systems
> which see heavy LRU lock contention benefit more
> - A larger page size has more internal fragmentation, so we run out of
> memory and have to do reclaim more often (and maybe workload which
> used to fit in DRAM now do not)
> (probably others; i'm not at 100% right now)
>
> I think concerns about "allocating lots of order-2 folios makes it harder
> to allocate order-4 folios" are _probably_ not warranted (without data
> to prove otherwise). All anonymous memory is movable, so our compaction
> code should be able to create larger order folios.
>
next prev parent reply other threads:[~2023-07-07 10:00 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 13:53 [PATCH v2 0/5] variable-order, large folios for anonymous memory Ryan Roberts
2023-07-03 13:53 ` [PATCH v2 1/5] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap() Ryan Roberts
2023-07-03 19:05 ` Yu Zhao
2023-07-04 2:13 ` Yin, Fengwei
2023-07-04 11:19 ` Ryan Roberts
2023-07-04 2:14 ` Yin, Fengwei
2023-07-03 13:53 ` [PATCH v2 2/5] mm: Allow deferred splitting of arbitrary large anon folios Ryan Roberts
2023-07-07 8:21 ` Huang, Ying
2023-07-07 9:42 ` Ryan Roberts
2023-07-10 5:37 ` Huang, Ying
2023-07-10 8:29 ` Ryan Roberts
2023-07-10 9:01 ` Huang, Ying
2023-07-10 9:39 ` Ryan Roberts
2023-07-11 1:56 ` Huang, Ying
2023-07-03 13:53 ` [PATCH v2 3/5] mm: Default implementation of arch_wants_pte_order() Ryan Roberts
2023-07-03 19:50 ` Yu Zhao
2023-07-04 13:20 ` Ryan Roberts
2023-07-05 2:07 ` Yu Zhao
2023-07-05 9:11 ` Ryan Roberts
2023-07-05 17:24 ` Yu Zhao
2023-07-05 18:01 ` Ryan Roberts
2023-07-06 19:33 ` Matthew Wilcox
2023-07-07 10:00 ` Ryan Roberts [this message]
2023-07-04 2:22 ` Yin, Fengwei
2023-07-04 3:02 ` Yu Zhao
2023-07-04 3:59 ` Yu Zhao
2023-07-04 5:22 ` Yin, Fengwei
2023-07-04 5:42 ` Yu Zhao
2023-07-04 12:36 ` Ryan Roberts
2023-07-04 13:23 ` Ryan Roberts
2023-07-05 1:40 ` Yu Zhao
2023-07-05 1:23 ` Yu Zhao
2023-07-05 2:18 ` Yin Fengwei
2023-07-03 13:53 ` [PATCH v2 4/5] mm: FLEXIBLE_THP for improved performance Ryan Roberts
2023-07-03 15:51 ` kernel test robot
2023-07-03 16:01 ` kernel test robot
2023-07-04 1:35 ` Yu Zhao
2023-07-04 14:08 ` Ryan Roberts
2023-07-04 23:47 ` Yu Zhao
2023-07-04 3:45 ` Yin, Fengwei
2023-07-04 14:20 ` Ryan Roberts
2023-07-04 23:35 ` Yin Fengwei
2023-07-04 23:57 ` Matthew Wilcox
2023-07-05 9:54 ` Ryan Roberts
2023-07-05 12:08 ` Matthew Wilcox
2023-07-07 8:01 ` Huang, Ying
2023-07-07 9:52 ` Ryan Roberts
2023-07-07 11:29 ` David Hildenbrand
2023-07-07 13:57 ` Matthew Wilcox
2023-07-07 14:07 ` David Hildenbrand
2023-07-07 15:13 ` Ryan Roberts
2023-07-07 16:06 ` David Hildenbrand
2023-07-07 16:22 ` Ryan Roberts
2023-07-07 19:06 ` David Hildenbrand
2023-07-10 8:41 ` Ryan Roberts
2023-07-10 3:03 ` Huang, Ying
2023-07-10 8:55 ` Ryan Roberts
2023-07-10 9:18 ` Huang, Ying
2023-07-10 9:25 ` Ryan Roberts
2023-07-11 0:48 ` Huang, Ying
2023-07-10 2:49 ` Huang, Ying
2023-07-03 13:53 ` [PATCH v2 5/5] arm64: mm: Override arch_wants_pte_order() Ryan Roberts
2023-07-03 20:02 ` Yu Zhao
2023-07-04 2:18 ` [PATCH v2 0/5] variable-order, large folios for anonymous memory Yu Zhao
2023-07-04 6:22 ` Yin, Fengwei
2023-07-04 7:11 ` Yu Zhao
2023-07-04 15:36 ` Ryan Roberts
2023-07-04 23:52 ` Yin Fengwei
2023-07-05 0:21 ` Yu Zhao
2023-07-05 10:16 ` Ryan Roberts
2023-07-05 19:00 ` Yu Zhao
2023-07-05 19:38 ` David Hildenbrand
2023-07-06 8:02 ` Ryan Roberts
2023-07-07 11:40 ` David Hildenbrand
2023-07-07 13:12 ` Matthew Wilcox
2023-07-07 13:24 ` David Hildenbrand
2023-07-10 10:07 ` Ryan Roberts
2023-07-10 16:57 ` Matthew Wilcox
2023-07-10 16:53 ` Zi Yan
2023-07-19 15:49 ` Ryan Roberts
2023-07-19 16:05 ` Zi Yan
2023-07-19 18:37 ` Ryan Roberts
2023-07-11 21:11 ` Luis Chamberlain
2023-07-11 21:59 ` Matthew Wilcox
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