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From: Florian Weimer <fweimer@redhat•com>
To: linuxppc-dev@lists•ozlabs.org
Cc: Peter Bergner <bergner@linux•ibm.com>
Subject: Are 256K page sizes really a thing (on ppc64le in particular)?
Date: Sat, 28 Sep 2024 18:08:23 +0200	[thread overview]
Message-ID: <87cyknzrpk.fsf@oldenburg.str.redhat.com> (raw)

I'm working on adding a <sys/pagesize.h> header to glibc, so that
programmers can easily determine the range of possible page sizes for a
particular target, for things like pointer tagging and mapped file
alignment requirements.

I'm not familiar from the Kconfig system, but as far as I can tell, this
ensures that 256 KiB pages are only available on 44x machines:

arch/powerpc/Kconfig-config PPC_256K_PAGES
arch/powerpc/Kconfig-   bool "256k page size (Requires non-standard binutils settings)"
arch/powerpc/Kconfig-   depends on 44x && !PPC_47x
arch/powerpc/Kconfig:   select HAVE_PAGE_SIZE_256KB

And none of the 44x configurations set 64BIT, so it's all 32-bit.

Would it still make sense to recommend 256 KiB file alignment to
programmers on 32-bit PowerPC, or should <sys/pagesize.h> pretend
that the maximum page size is 64 KiB?

Thanks,
Florian

next             reply	other threads:[~2024-09-28 16:08 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-09-28 16:08 Florian Weimer [this message]
2024-09-28 16:38 ` Are 256K page sizes really a thing (on ppc64le in particular)? LEROY Christophe
2024-09-29 11:24   ` Michael Ellerman

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