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Date: Fri, 16 Feb 2024 12:30:48 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
	Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	David Hildenbrand <david@redhat.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	John Hubbard <jhubbard@nvidia.com>, Zi Yan <ziy@nvidia.com>,
	Barry Song <21cnbao@gmail.com>,
	Alistair Popple <apopple@nvidia.com>,
	Yang Shi <shy828301@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-arm-kernel@lists.infradead.org, x86@kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 14/18] arm64/mm: Implement new
 [get_and_]clear_full_ptes() batch APIs
Message-ID: <Zc9VeMJpdpJG9LsH@arm.com>
References: <20240215103205.2607016-1-ryan.roberts@arm.com>
 <20240215103205.2607016-15-ryan.roberts@arm.com>
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In-Reply-To: <20240215103205.2607016-15-ryan.roberts@arm.com>

On Thu, Feb 15, 2024 at 10:32:01AM +0000, Ryan Roberts wrote:
> Optimize the contpte implementation to fix some of the
> exit/munmap/dontneed performance regression introduced by the initial
> contpte commit. Subsequent patches will solve it entirely.
> 
> During exit(), munmap() or madvise(MADV_DONTNEED), mappings must be
> cleared. Previously this was done 1 PTE at a time. But the core-mm
> supports batched clear via the new [get_and_]clear_full_ptes() APIs. So
> let's implement those APIs and for fully covered contpte mappings, we no
> longer need to unfold the contpte. This significantly reduces unfolding
> operations, reducing the number of tlbis that must be issued.
> 
> Tested-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>