Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory

From: Matthew Wilcox <willy@infradead.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Yin Fengwei <fengwei.yin@intel.com>,
	David Hildenbrand <david@redhat.com>, Yu Zhao <yuzhao@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Yang Shi <shy828301@gmail.com>,
	"Huang, Ying" <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Itaru Kitayama <itaru.kitayama@gmail.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>, Hugh Dickins <hughd@google.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory
Date: Mon, 13 Nov 2023 05:18:08 +0000	[thread overview]
Message-ID: <ZVGxkMeY50JSesaj@casper.infradead.org> (raw)
In-Reply-To: <c507308d-bdd4-5f9e-d4ff-e96e4520be85@nvidia.com>

On Sun, Nov 12, 2023 at 10:57:47PM -0500, John Hubbard wrote:
> I've done some initial performance testing of this patchset on an arm64
> SBSA server. When these patches are combined with the arm64 arch contpte
> patches in Ryan's git tree (he has conveniently combined everything
> here: [1]), we are seeing a remarkable, consistent speedup of 10.5x on
> some memory-intensive workloads. Many test runs, conducted independently
> by different engineers and on different machines, have convinced me and
> my colleagues that this is an accurate result.
> 
> In order to achieve that result, we used the git tree in [1] with
> following settings:
> 
>     echo always >/sys/kernel/mm/transparent_hugepage/enabled
>     echo recommend >/sys/kernel/mm/transparent_hugepage/anon_orders
> 
> This was on a aarch64 machine configure to use a 64KB base page size.
> That configuration means that the PMD size is 512MB, which is of course
> too large for practical use as a pure PMD-THP. However, with with these
> small-size (less than PMD-sized) THPs, we get the improvements in TLB
> coverage, while still getting pages that are small enough to be
> effectively usable.

That is quite remarkable!

My hope is to abolish the 64kB page size configuration.  ie instead of
using the mixture of page sizes that you currently are -- 64k and
1M (right?  Order-0, and order-4), that 4k, 64k and 2MB (order-0,
order-4 and order-9) will provide better performance.

Have you run any experiements with a 4kB page size?

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