From: Mike Rapoport <rppt@kernel.org>
To: Vineet Gupta <vgupta@kernel.org>
Cc: linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH 09/18] ARC: mm: non-functional code cleanup ahead of 3 levels
Date: Thu, 12 Aug 2021 09:18:34 +0300 [thread overview]
Message-ID: <YRS9OvkgaQxOfkkg@kernel.org> (raw)
In-Reply-To: <7d022d55-c70b-b3ac-4f0b-1faa26c0d4bd@kernel.org>
On Wed, Aug 11, 2021 at 06:37:19PM -0700, Vineet Gupta wrote:
> On 8/11/21 5:31 AM, Mike Rapoport wrote:
> > > +/*
> > > + * For ARC, pgtable_t is not struct page *, but pte_t * (to avoid
> > > + * extraneous page_address() calculations) hence can't use
> > > + * use asm-generic/pgalloc.h which assumes it being struct page *
> > > + */
> > Another reason to leave ARC without asm-generic/pgalloc.h was
> > __get_order_pte() that other arches don't have.
> > So this and pgtable_t aliased to pte_t * seemed to me too much to bother
> > then, but probably it's worth reconsidering with addition of 3rd and 4th
> > levels.
>
> I agree that savings of not havign page_address() might not be huge. However
> asm-generic/pgalloc.h only has pte allocation routines and all other
> allocation levels come from arch file
asm-generic/pgalloc.h has allocation routines up to PUD.
There is also pgtable_pmd_page_ctor() and pgtable_pmd_page_dtor() called in
the generic versions of PMD allocation, it seems they are not called in ARC
implementation.
So using asm-generic/pgalloc.h would probably save you some THP debugging ;-)
We may even probably accommodate multi-page PTEs in asm-generic/pgalloc.h
with something like
#ifndef __HAVE_ARCH_PTE_GET_ORDER
static inline int __pte_get_order(void)
{
return 0;
}
#endif
> Also for ARCv2, given the arbitrary address split and ensuing paging levels
> (as well as support for different page sizes) we will need to make sure that
> one page is enough to hold any level's paging using say BUILD_BUG_ON. In
> fact that should also be done for 3rd and 4th levels for sanity.
Right, these sanity checks would be useful, but they may live in one of .c
files in arch/arc/mm.
> -Vineet
>
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2021-08-12 6:18 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 0:42 [PATCH 00/18] ARC mm updates to support 3 or 4 levels of paging Vineet Gupta
2021-08-11 0:42 ` [PATCH 01/18] ARC: mm: simplify mmu scratch register assingment to mmu needs Vineet Gupta
2021-08-11 0:42 ` [PATCH 02/18] ARC: mm: remove tlb paranoid code Vineet Gupta
2021-08-11 0:42 ` [PATCH 03/18] ARC: mm: move mmu/cache externs out to setup.h Vineet Gupta
2021-08-11 5:10 ` Mike Rapoport
2021-08-11 18:46 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 04/18] ARC: mm: remove pgd_offset_fast Vineet Gupta
2021-08-11 5:12 ` Mike Rapoport
2021-08-11 18:54 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 05/18] ARC: mm: Fixes to allow STRICT_MM_TYPECHECKS Vineet Gupta
2021-08-11 0:42 ` [PATCH 06/18] ARC: mm: Enable STRICT_MM_TYPECHECKS Vineet Gupta
2021-08-11 12:04 ` Mike Rapoport
2021-08-11 19:01 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 07/18] ARC: ioremap: use more commonly used PAGE_KERNEL based uncached flag Vineet Gupta
2021-08-11 5:18 ` Mike Rapoport
2021-08-11 18:58 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 08/18] ARC: mm: pmd_populate* to use the canonical set_pmd (and drop pmd_set) Vineet Gupta
2021-08-11 0:42 ` [PATCH 09/18] ARC: mm: non-functional code cleanup ahead of 3 levels Vineet Gupta
2021-08-11 12:31 ` Mike Rapoport
2021-08-12 1:37 ` Vineet Gupta
2021-08-12 6:18 ` Mike Rapoport [this message]
2021-08-12 18:58 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 10/18] ARC: mm: move MMU specific bits out of ASID allocator Vineet Gupta
2021-08-11 0:42 ` [PATCH 11/18] ARC: mm: move MMU specific bits out of entry code Vineet Gupta
2021-08-11 12:15 ` Mike Rapoport
2021-08-11 19:30 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 12/18] ARC: mm: disintegrate mmu.h (arcv2 bits out) Vineet Gupta
2021-08-11 0:42 ` [PATCH 13/18] ARC: mm: disintegrate pgtable.h into levels and flags Vineet Gupta
2021-08-11 0:42 ` [PATCH 14/18] ARC: mm: hack to allow 2 level build with 4 level code Vineet Gupta
2021-08-11 0:42 ` [PATCH 15/18] ARC: mm: support 3 levels of page tables Vineet Gupta
2021-08-11 12:24 ` Mike Rapoport
2021-08-11 22:15 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 16/18] ARC: mm: support 4 " Vineet Gupta
2021-08-11 12:28 ` Mike Rapoport
2021-08-11 22:17 ` Vineet Gupta
2021-08-11 0:42 ` [PATCH 17/18] ARC: mm: vmalloc sync from kernel to user table to update PMD Vineet Gupta
2021-08-11 0:42 ` [PATCH 18/18] ARC: mm: introduce _PAGE_TABLE to explicitly link pgd,pud,pmd entries Vineet Gupta
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