From: Catalin Marinas <catalin.marinas@arm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Sudarshan Rajagopalan <sudaraja@codeaurora.org>,
linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
David Hildenbrand <david@redhat.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Mark Rutland <mark.rutland@arm.com>,
Logan Gunthorpe <logang@deltatee.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Price <steven.price@arm.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS
Date: Thu, 21 Jan 2021 15:54:10 +0000 [thread overview]
Message-ID: <20210121155410.GH21811@gaia> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2101211004540.100764@www.lameter.com>
On Thu, Jan 21, 2021 at 10:08:17AM +0000, Christoph Lameter wrote:
> On Wed, 20 Jan 2021, Sudarshan Rajagopalan wrote:
>
> > But there are other problems in reducing SECTION_SIZE_BIT. Reducing it by too
> > much would over populate /sys/devices/system/memory/ and also consume too many
> > page->flags bits in the !vmemmap case. Also section size needs to be multiple
> > of 128MB to have PMD based vmemmap mapping with CONFIG_ARM64_4K_PAGES.
>
> There is also the issue of requiring more space in the TLB cache with
> smaller page sizes. Or does ARM resolve these into smaller TLB entries
> anyways (going on my x86 kwon how here)? Anyways if there are only a few
> TLB entries then the effect could
> be significant.
There is indeed more TLB pressure with smaller page sizes but this patch
doesn't change this.
--
Catalin
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Logan Gunthorpe <logang@deltatee.com>,
Sudarshan Rajagopalan <sudaraja@codeaurora.org>,
David Hildenbrand <david@redhat.com>,
linux-kernel@vger.kernel.org, Mike Rapoport <rppt@linux.ibm.com>,
Suren Baghdasaryan <surenb@google.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Steven Price <steven.price@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/1] arm64/sparsemem: reduce SECTION_SIZE_BITS
Date: Thu, 21 Jan 2021 15:54:10 +0000 [thread overview]
Message-ID: <20210121155410.GH21811@gaia> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2101211004540.100764@www.lameter.com>
On Thu, Jan 21, 2021 at 10:08:17AM +0000, Christoph Lameter wrote:
> On Wed, 20 Jan 2021, Sudarshan Rajagopalan wrote:
>
> > But there are other problems in reducing SECTION_SIZE_BIT. Reducing it by too
> > much would over populate /sys/devices/system/memory/ and also consume too many
> > page->flags bits in the !vmemmap case. Also section size needs to be multiple
> > of 128MB to have PMD based vmemmap mapping with CONFIG_ARM64_4K_PAGES.
>
> There is also the issue of requiring more space in the TLB cache with
> smaller page sizes. Or does ARM resolve these into smaller TLB entries
> anyways (going on my x86 kwon how here)? Anyways if there are only a few
> TLB entries then the effect could
> be significant.
There is indeed more TLB pressure with smaller page sizes but this patch
doesn't change this.
--
Catalin
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-01-21 15:57 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 5:29 [PATCH 0/1] arm64/sparsemem: reduce SECTION_SIZE_BITS Sudarshan Rajagopalan
2021-01-21 5:29 ` [PATCH 1/1] " Sudarshan Rajagopalan
2021-01-21 10:08 ` Christoph Lameter
2021-01-21 10:08 ` Christoph Lameter
2021-01-21 10:08 ` Christoph Lameter
2021-01-21 15:54 ` Catalin Marinas [this message]
2021-01-21 15:54 ` Catalin Marinas
2021-01-21 13:36 ` Will Deacon
2021-01-21 13:36 ` Will Deacon
2021-01-22 2:58 ` Anshuman Khandual
2021-01-22 2:58 ` Anshuman Khandual
2021-01-21 13:45 ` David Hildenbrand
2021-01-21 13:45 ` David Hildenbrand
2021-01-21 14:16 ` Mike Rapoport
2021-01-21 14:16 ` Mike Rapoport
2021-01-21 16:04 ` David Hildenbrand
2021-01-21 16:04 ` David Hildenbrand
2021-01-21 15:51 ` Catalin Marinas
2021-01-21 15:51 ` Catalin Marinas
2021-01-21 18:26 ` [PATCH 0/1] " Will Deacon
2021-01-21 18:26 ` Will Deacon
2021-01-29 0:17 ` Pavel Tatashin
2021-01-29 0:17 ` Pavel Tatashin
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