From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Arnd Bergmann <arnd@arndb.de>,
Samuel Holland <samuel.holland@sifive.com>,
Arnd Bergmann <arnd@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
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Cc: Matt Turner <mattst88@gmail.com>,
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Subject: Re: [PATCH 1/4] arch: consolidate existing CONFIG_PAGE_SIZE_*KB definitions
Date: Tue, 27 Feb 2024 15:44:31 +0000 [thread overview]
Message-ID: <b737a088-c811-45eb-b143-d24e6cdf7eea@csgroup.eu> (raw)
In-Reply-To: <83450530-c908-4abc-bab7-88c50a3143ff@app.fastmail.com>
Le 27/02/2024 à 16:40, Arnd Bergmann a écrit :
> On Mon, Feb 26, 2024, at 17:55, Samuel Holland wrote:
>> On 2024-02-26 10:14 AM, Arnd Bergmann wrote:
>>>
>>> +config HAVE_PAGE_SIZE_4KB
>>> + bool
>>> +
>>> +config HAVE_PAGE_SIZE_8KB
>>> + bool
>>> +
>>> +config HAVE_PAGE_SIZE_16KB
>>> + bool
>>> +
>>> +config HAVE_PAGE_SIZE_32KB
>>> + bool
>>> +
>>> +config HAVE_PAGE_SIZE_64KB
>>> + bool
>>> +
>>> +config HAVE_PAGE_SIZE_256KB
>>> + bool
>>> +
>>> +choice
>>> + prompt "MMU page size"
>>
>> Should this have some generic help text (at least a warning about
>> compatibility)?
>
> Good point. I've added some of this now, based on the mips
> text with some generalizations for other architectures:
>
> config PAGE_SIZE_4KB
> bool "4KiB pages"
> depends on HAVE_PAGE_SIZE_4KB
> help
> This option select the standard 4KiB Linux page size and the only
> available option on many architectures. Using 4KiB page size will
> minimize memory consumption and is therefore recommended for low
> memory systems.
> Some software that is written for x86 systems makes incorrect
> assumptions about the page size and only runs on 4KiB pages.
>
> config PAGE_SIZE_8KB
> bool "8KiB pages"
> depends on HAVE_PAGE_SIZE_8KB
> help
> This option is the only supported page size on a few older
> processors, and can be slightly faster than 4KiB pages.
>
> config PAGE_SIZE_16KB
> bool "16KiB pages"
> depends on HAVE_PAGE_SIZE_16KB
> help
> This option is usually a good compromise between memory
> consumption and performance for typical desktop and server
> workloads, often saving a level of page table lookups compared
> to 4KB pages as well as reducing TLB pressure and overhead of
> per-page operations in the kernel at the expense of a larger
> page cache.
>
> config PAGE_SIZE_32KB
> bool "32KiB pages"
> depends on HAVE_PAGE_SIZE_32KB
> Using 32KiB page size will result in slightly higher performance
> kernel at the price of higher memory consumption compared to
> 16KiB pages. This option is available only on cnMIPS cores.
> Note that you will need a suitable Linux distribution to
> support this.
>
> config PAGE_SIZE_64KB
> bool "64KiB pages"
> depends on HAVE_PAGE_SIZE_64KB
> Using 64KiB page size will result in slightly higher performance
> kernel at the price of much higher memory consumption compared to
> 4KiB or 16KiB pages.
> This is not suitable for general-purpose workloads but the
> better performance may be worth the cost for certain types of
> supercomputing or database applications that work mostly with
> large in-memory data rather than small files.
>
> config PAGE_SIZE_256KB
> bool "256KiB pages"
> depends on HAVE_PAGE_SIZE_256KB
> help
> 256KB pages have little practical value due to their extreme
> memory usage.
For 256K pages, powerpc has the following help. I think you should have
it too:
The kernel will only be able to run applications that have been
compiled with '-zmax-page-size' set to 256K (the default is 64K) using
binutils later than 2.17.50.0.3, or by patching the ELF_MAXPAGESIZE
definition from 0x10000 to 0x40000 in older versions.
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next prev parent reply other threads:[~2024-02-27 15:44 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 16:14 [PATCH 0/4] arch: mm, vdso: consolidate PAGE_SIZE definition Arnd Bergmann
2024-02-26 16:14 ` [PATCH 1/4] arch: consolidate existing CONFIG_PAGE_SIZE_*KB definitions Arnd Bergmann
2024-02-26 16:55 ` Samuel Holland
2024-02-27 15:40 ` Arnd Bergmann
2024-02-27 15:44 ` Christophe Leroy [this message]
2024-02-27 15:48 ` Arnd Bergmann
2024-02-26 19:02 ` Christophe Leroy
2024-02-27 15:42 ` Arnd Bergmann
2024-02-27 8:45 ` Geert Uytterhoeven
2024-02-27 15:43 ` Arnd Bergmann
2024-02-26 16:14 ` [PATCH 2/4] arch: simplify architecture specific page size configuration Arnd Bergmann
2024-02-26 19:05 ` Christophe Leroy
2024-02-27 13:46 ` Catalin Marinas
2024-02-27 13:53 ` Helge Deller
2024-02-26 16:14 ` [PATCH 3/4] arch: define CONFIG_PAGE_SIZE_*KB on all architectures Arnd Bergmann
2024-02-27 0:49 ` Guo Ren
2024-02-27 7:41 ` Heiko Carstens
2024-02-27 8:54 ` Geert Uytterhoeven
2024-02-27 10:59 ` Arnd Bergmann
2024-02-27 11:12 ` Geert Uytterhoeven
2024-02-27 14:18 ` Arnd Bergmann
2024-02-28 21:06 ` Stafford Horne
2024-03-05 10:59 ` Johannes Berg
2024-02-26 16:14 ` [PATCH 4/4] vdso: avoid including asm/page.h Arnd Bergmann
2024-02-26 18:53 ` Christophe Leroy
2024-02-27 12:57 ` Michael Ellerman
2024-02-27 13:46 ` Catalin Marinas
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