From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 4/7] Store huge page linux pte in mm_struct
Date: Mon, 6 Feb 2012 10:29:57 +0000 [thread overview]
Message-ID: <20120206102957.GB26538@arm.com> (raw)
In-Reply-To: <4F2F352B.9080408@gmail.com>
bill4carson wrote:
> Normal page based pte has hardware version and linux version, these
> two kinds of ptes occupy half of 4K page, and each of two pmd level
> entry pointer to this half 4K page.
>
> For huge page, mappings only exist in pmd level from hardware
> perspective, however mm subsystem also needs to know the linux version
> *pte* of this huge page based mapping, problems is where to store
> these huge page linux pte?
>
> A:
> Store huge page linux pte in mm_struct
>
> B:
> Store huge page linux pte in mm_context_t suggested by Catalin.
> This is almost like option A, while it's nice to modify arm code only
> and take small effort to make it happen.
>
> C:
> Modify pgd_alloc to allocate 2048 pgd_t entries plus two void pointers
> Use these two additional pointers to store huge page linux pte.
> It's feasible, but I don't know whether this is a good idea.
I wouldn't add this to pgd_alloc since not all tasks need huge pages.
First option is also not feasible as we shouldn't touch generic code.
This leaves us with B, unless better options are suggested.
I had a patch couple of years ago
(http://article.gmane.org/gmane.linux.ports.arm.kernel/55045) to use the
AF (Access Flag) bit and free up some bits in the page table, allowing
us to drop the Linux PTE. But we end up in a bigger configuration mess
as we already have to choose between classic MMU and LPAE. The
performance advantage wasn't that big either.
--
Catalin
next prev parent reply other threads:[~2012-02-06 10:29 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 7:57 [RFC] ARM hugetlb support bill4carson at gmail.com
2012-01-30 7:57 ` [PATCH 1/7] Add various hugetlb arm high level hooks bill4carson at gmail.com
2012-02-06 17:07 ` Catalin Marinas
2012-02-07 2:00 ` bill4carson
2012-02-07 11:54 ` Catalin Marinas
2012-02-07 12:15 ` Catalin Marinas
2012-02-07 12:57 ` carson bill
2012-01-30 7:57 ` [PATCH 2/7] Add various hugetlb page table fix bill4carson at gmail.com
2012-01-31 9:57 ` Catalin Marinas
2012-01-31 9:58 ` Russell King - ARM Linux
2012-01-31 12:25 ` Catalin Marinas
2012-02-01 3:10 ` bill4carson
2012-02-06 16:26 ` Catalin Marinas
2012-02-07 1:42 ` bill4carson
2012-02-07 11:50 ` Catalin Marinas
2012-02-07 13:24 ` carson bill
2012-02-07 14:11 ` Catalin Marinas
2012-02-07 14:46 ` carson bill
2012-02-07 15:09 ` Catalin Marinas
2012-02-07 15:41 ` carson bill
2012-01-30 7:57 ` [PATCH 3/7] Introduce set_hugepte_ext api for huge page hardware page table setup bill4carson at gmail.com
2012-01-30 7:57 ` [PATCH 4/7] Store huge page linux pte in mm_struct bill4carson at gmail.com
2012-01-31 9:37 ` Catalin Marinas
2012-01-31 10:01 ` Russell King - ARM Linux
2012-02-01 5:45 ` bill4carson
2012-02-06 2:04 ` bill4carson
2012-02-06 10:29 ` Catalin Marinas [this message]
2012-02-06 14:40 ` carson bill
2012-01-30 7:57 ` [PATCH 5/7] Using do_page_fault for section fault handling bill4carson at gmail.com
2012-01-30 7:57 ` [PATCH 6/7] Add hugetlb Kconfig option bill4carson at gmail.com
2012-01-30 7:57 ` [PATCH 7/7] Minor compiling fix bill4carson at gmail.com
2012-01-31 9:29 ` [RFC] ARM hugetlb support Catalin Marinas
2012-02-01 1:56 ` bill4carson
2012-02-02 14:38 ` Catalin Marinas
2012-02-03 1:41 ` bill4carson
2012-02-06 16:29 ` Catalin Marinas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120206102957.GB26538@arm.com \
--to=catalin.marinas@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox