From: Andrew Morton <akpm@linux-foundation.org>
To: Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>
Cc: linux-mm@kvack.org, mpe@ellerman.id.au,
linuxppc-dev@lists.ozlabs.org, npiggin@gmail.com,
christophe.leroy@csgroup.eu, Oscar Salvador <osalvador@suse.de>,
Mike Kravetz <mike.kravetz@oracle.com>,
Dan Williams <dan.j.williams@intel.com>,
Joao Martins <joao.m.martins@oracle.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Muchun Song <muchun.song@linux.dev>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH v6 00/13] Add support for DAX vmemmap optimization for ppc64
Date: Wed, 26 Jul 2023 11:52:46 -0700 [thread overview]
Message-ID: <20230726115246.b6ed2a08aa7b648671107a8a@linux-foundation.org> (raw)
In-Reply-To: <47feb4fe-f461-a2c2-1368-5480d00d0f1d@linux.ibm.com>
On Wed, 26 Jul 2023 10:59:32 +0530 Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> wrote:
> On 7/26/23 12:59 AM, Andrew Morton wrote:
> > On Tue, 25 Jul 2023 00:37:46 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote:
> >
> >> This patch series implements changes required to support DAX vmemmap
> >> optimization for ppc64.
> >
> > Do we have any measurements to help us understand the magnitude
> > of this optimization?
> >
> > And any documentation which helps users understand whether and
> > why they should enable this feature?
>
> That is memory space optimization due to kernel reusing the tail page struct pages. The details
> of the optimization is documented in patch 11. We document there the impact with both 4k and
> 64K page size.
I suppose that with sufficient arithmetic one could use
Documentation/powerpc/vmemmap_dedup.rst to figure out the bottom-line
savings.
I was more expecting a straightforward statement in the [0/N] overview
to help people understand why they're reading this patchset at all.
Like "saves 5% of total memory on my XXX machine".
next prev parent reply other threads:[~2023-07-26 18:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-24 19:07 [PATCH v6 00/13] Add support for DAX vmemmap optimization for ppc64 Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 01/13] mm/hugepage pud: Allow arch-specific helper function to check huge page pud support Aneesh Kumar K.V
2023-07-26 10:52 ` [PATCH v6 01/13 -fix] " Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 03/13] mm/vmemmap: Improve vmemmap_can_optimize and allow architectures to override Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 04/13] mm/vmemmap: Allow architectures to override how vmemmap optimization works Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 05/13] mm: Add pud_same similar to __HAVE_ARCH_P4D_SAME Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 07/13] mm/vmemmap optimization: Split hugetlb and devdax vmemmap optimization Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 08/13] powerpc/mm/trace: Convert trace event to trace event class Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 09/13] powerpc/book3s64/mm: Enable transparent pud hugepage Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 10/13] powerpc/book3s64/vmemmap: Switch radix to use a different vmemmap handling function Aneesh Kumar K.V
2023-07-27 5:06 ` [PATCH v6 10/13 -fix] " Aneesh Kumar K.V
2023-07-28 10:22 ` [PATCH v6 10/13 -fix2] " Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 11/13] powerpc/book3s64/radix: Add support for vmemmap optimization for radix Aneesh Kumar K.V
2023-07-26 14:05 ` [PATCH v6 11/13 -fix] " Aneesh Kumar K.V
2023-07-24 19:07 ` [PATCH v6 13/13] powerpc/book3s64/radix: Add debug message to give more details of vmemmap allocation Aneesh Kumar K.V
2023-07-25 19:29 ` [PATCH v6 00/13] Add support for DAX vmemmap optimization for ppc64 Andrew Morton
2023-07-26 5:29 ` Aneesh Kumar K V
2023-07-26 18:52 ` Andrew Morton [this message]
2023-07-27 5:37 ` Aneesh Kumar K.V
[not found] ` <20230724190759.483013-13-aneesh.kumar@linux.ibm.com>
2023-07-28 10:23 ` [PATCH v6 12/13 -fix] powerpc/book3s64/radix: Remove mmu_vmemmap_psize Aneesh Kumar K.V
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