From: Yu Zhao <yuzhao@google.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.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 0/5] variable-order, large folios for anonymous memory
Date: Mon, 3 Jul 2023 20:18:50 -0600 [thread overview]
Message-ID: <CAOUHufYB2kB0r9hhSbzfEzdF85MkXVfWoFOhy3LwLfJ5Qo8H6g@mail.gmail.com> (raw)
In-Reply-To: <20230703135330.1865927-1-ryan.roberts@arm.com>
On Mon, Jul 3, 2023 at 7:53 AM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> Hi All,
>
> This is v2 of a series to implement variable order, large folios for anonymous
> memory. The objective of this is to improve performance by allocating larger
> chunks of memory during anonymous page faults. See [1] for background.
Thanks for the quick response!
> I've significantly reworked and simplified the patch set based on comments from
> Yu Zhao (thanks for all your feedback!). I've also renamed the feature to
> VARIABLE_THP, on Yu's advice.
>
> The last patch is for arm64 to explicitly override the default
> arch_wants_pte_order() and is intended as an example. If this series is accepted
> I suggest taking the first 4 patches through the mm tree and the arm64 change
> could be handled through the arm64 tree separately. Neither has any build
> dependency on the other.
>
> The one area where I haven't followed Yu's advice is in the determination of the
> size of folio to use. It was suggested that I have a single preferred large
> order, and if it doesn't fit in the VMA (due to exceeding VMA bounds, or there
> being existing overlapping populated PTEs, etc) then fallback immediately to
> order-0. It turned out that this approach caused a performance regression in the
> Speedometer benchmark.
I suppose it's regression against the v1, not the unpatched kernel.
> With my v1 patch, there were significant quantities of
> memory which could not be placed in the 64K bucket and were instead being
> allocated for the 32K and 16K buckets. With the proposed simplification, that
> memory ended up using the 4K bucket, so page faults increased by 2.75x compared
> to the v1 patch (although due to the 64K bucket, this number is still a bit
> lower than the baseline). So instead, I continue to calculate a folio order that
> is somewhere between the preferred order and 0. (See below for more details).
I suppose the benchmark wasn't running under memory pressure, which is
uncommon for client devices. It could be easier the other way around:
using 32/16KB shows regression whereas order-0 shows better
performance under memory pressure.
I'm not sure we should use v1 as the baseline. Unpatched kernel sounds
more reasonable at this point. If 32/16KB is proven to be better in
most scenarios including under memory pressure, we can reintroduce
that policy. I highly doubt this is the case: we tried 16KB base page
size on client devices, and overall, the regressions outweighs the
benefits.
> The patches are based on top of v6.4 plus Matthew Wilcox's set_ptes() series
> [2], which is a hard dependency. I have a branch at [3].
It's not clear to me why [2] is a hard dependency.
It seems to me we are getting close and I was hoping we could get into
mm-unstable soon without depending on other series...
next prev parent reply other threads:[~2023-07-04 2:19 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
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 ` Yu Zhao [this message]
2023-07-04 6:22 ` [PATCH v2 0/5] variable-order, large folios for anonymous memory 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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