From: Vineet Gupta <vgupta@kernel.org>
To: Mike Rapoport <rppt@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 11:58:03 -0700 [thread overview]
Message-ID: <f77ac5df-c92c-321a-7624-35520b386f6f@kernel.org> (raw)
In-Reply-To: <YRS9OvkgaQxOfkkg@kernel.org>
On 8/11/21 11:18 PM, Mike Rapoport wrote:
> 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
Not needed - those cases are unreal, esoteric at best. I'm working on
switching back to canonical struct page based pgtable_t, will do that in v2.
>> 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.
Sure !
Thx,
-Vineet
next prev parent reply other threads:[~2021-08-12 18:58 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
2021-08-12 18:58 ` Vineet Gupta [this message]
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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