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From: Dan Williams <dan.j.williams@intel.com>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Linux MM <linux-mm@kvack.org>,
	Linux NVDIMM <nvdimm@lists.linux.dev>,
	 Ira Weiny <ira.weiny@intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	 Jason Gunthorpe <jgg@ziepe.ca>, Jane Chu <jane.chu@oracle.com>,
	 Muchun Song <songmuchun@bytedance.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	 Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v1 09/11] mm/page_alloc: reuse tail struct pages for compound pagemaps
Date: Mon, 7 Jun 2021 12:32:47 -0700	[thread overview]
Message-ID: <CAPcyv4hJtqVGoA3ppCMfVQ4ZnWUa7jKtp=Huxu9mcSk4huq_7Q@mail.gmail.com> (raw)
In-Reply-To: <840290bd-55cc-e77a-b13d-05c6fd361865@oracle.com>

On Mon, Jun 7, 2021 at 6:49 AM Joao Martins <joao.m.martins@oracle.com> wrote:
[..]
> > Given all of the above I'm wondering if there should be a new
> > "compound specific" flavor of this routine rather than trying to
> > cleverly inter mingle the old path with the new. This is easier
> > because you have already done the work in previous patches to break
> > this into helpers. So just have memmap_init_zone_device() do it the
> > "old" way and memmap_init_compound() handle all the tail page init +
> > optimizations.
> >
> I can separate it out, should be easier to follow.
>
> Albeit just a note, I think memmap_init_compound() should be the new normal as metadata
> more accurately represents what goes on the page tables. That's regardless of
> vmemmap-based gains, and hence why my train of thought was to not separate it.
>
> After this series, all devmap pages where @geometry matches @align will have compound
> pages be used instead. And we enable that in device-dax as first user (in the next patch).
> altmap or not so far just differentiates on the uniqueness of struct pages as the former
> doesn't reuse base pages that only contain tail pages and consequently makes us initialize
> all tail struct pages.

I think combining the cases into a common central routine makes the
code that much harder to maintain. A small duplication cost is worth
it in my opinion to help readability / maintainability.

  reply	other threads:[~2021-06-07 19:32 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-25 23:09 [PATCH v1 00/11] mm, sparse-vmemmap: Introduce " Joao Martins
2021-03-25 23:09 ` [PATCH v1 01/11] memory-failure: fetch compound_head after pgmap_pfn_valid() Joao Martins
2021-03-25 23:09 ` [PATCH v1 02/11] mm/page_alloc: split prep_compound_page into head and tail subparts Joao Martins
2021-03-25 23:09 ` [PATCH v1 03/11] mm/page_alloc: refactor memmap_init_zone_device() page init Joao Martins
2021-03-25 23:09 ` [PATCH v1 04/11] mm/memremap: add ZONE_DEVICE support for compound pages Joao Martins
     [not found]   ` <CAPcyv4gs_rHL7FPqyQEb3yT4jrv8Wo_xA2ojKsppoBfmDocq8A@mail.gmail.com>
     [not found]     ` <cd1c9849-8660-dbdc-718a-aa4ba5d48c01@oracle.com>
     [not found]       ` <CAPcyv4jG8+S6xJyp=1S2=dpit0Hs2+HgGwpWeRROCRuJnQYAxQ@mail.gmail.com>
     [not found]         ` <56a3e271-4ef8-ba02-639e-fd7fe7de7e36@oracle.com>
     [not found]           ` <8c922a58-c901-1ad9-5d19-1182bd6dea1e@oracle.com>
     [not found]             ` <CAPcyv4j_PdzytEeabe95FrUiNVNobdJRvUE9M9j0krKQ1defBg@mail.gmail.com>
     [not found]               ` <e22ef769-5eb2-1812-497f-6d069d632cd0@oracle.com>
2021-06-07 21:00                 ` Joao Martins
2021-06-07 21:57                   ` Dan Williams
2021-03-25 23:09 ` [PATCH v1 05/11] mm/sparse-vmemmap: add a pgmap argument to section activation Joao Martins
2021-03-25 23:09 ` [PATCH v1 06/11] mm/sparse-vmemmap: refactor vmemmap_populate_basepages() Joao Martins
2021-03-25 23:09 ` [PATCH v1 07/11] mm/sparse-vmemmap: populate compound pagemaps Joao Martins
2021-03-25 23:09 ` [PATCH v1 08/11] mm/sparse-vmemmap: use hugepages for PUD " Joao Martins
2021-03-25 23:09 ` [PATCH v1 09/11] mm/page_alloc: reuse tail struct pages for " Joao Martins
     [not found]   ` <CAPcyv4gtSqfmuAaX9cs63OvLkf-h4B_5fPiEnM9p9cqLZztXpg@mail.gmail.com>
2021-06-07 13:48     ` Joao Martins
2021-06-07 19:32       ` Dan Williams [this message]
2021-06-14 18:41         ` Joao Martins
2021-06-14 23:07           ` Dan Williams
2021-03-25 23:09 ` [PATCH v1 10/11] device-dax: compound pagemap support Joao Martins
     [not found]   ` <CAPcyv4jeY0K7ciWeCLjxXmiWs7NNeM-_zEdZ2XAdYnyZc9PvWA@mail.gmail.com>
2021-06-07 13:59     ` Joao Martins
2021-03-25 23:09 ` [PATCH v1 11/11] mm/gup: grab head page refcount once for group of subpages Joao Martins
2021-06-02  1:05   ` Dan Williams
2021-06-07 15:21     ` Joao Martins
2021-06-07 19:22       ` Dan Williams
2021-04-01  9:38 ` [PATCH v1 00/11] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins

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