Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>,
	 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Nicholas Piggin <npiggin@gmail.com>,
	Linux-Arch <linux-arch@vger.kernel.org>,
	 Linux MM <linux-mm@kvack.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	 Heiko Carstens <heiko.carstens@de.ibm.com>,
	Rik van Riel <riel@surriel.com>,
	 Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	 Linux-sh list <linux-sh@vger.kernel.org>,
	Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v6 10/18] sh/tlb: Convert SH to generic mmu_gather
Date: Thu, 5 Dec 2019 16:26:57 +0100
Message-ID: <CAMuHMdVQO6vMDuns7rwk8sD+cPhEVQjEU_DiKiTQn0NY2ppzag@mail.gmail.com> (raw)
In-Reply-To: <20191204164143.GB2810@hirez.programming.kicks-ass.net>

Hoi Peter,

On Wed, Dec 4, 2019 at 5:42 PM Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Dec 04, 2019 at 04:07:53PM +0100, Geert Uytterhoeven wrote:
> > On Wed, Dec 4, 2019 at 2:35 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > > Does this fare better?
> >
> > Yes. Migo-R is happy again.
> > Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> >
> > > --- a/arch/sh/include/asm/pgalloc.h
> > > +++ b/arch/sh/include/asm/pgalloc.h
> > > @@ -36,9 +36,7 @@ do {                                                  \
> > >  #if CONFIG_PGTABLE_LEVELS > 2
> > >  #define __pmd_free_tlb(tlb, pmdp, addr)                        \
> > >  do {                                                   \
> > > -       struct page *page = virt_to_page(pmdp);         \
> > > -       pgtable_pmd_page_dtor(page);                    \
> > > -       tlb_remove_page((tlb), page);                   \
> > > +       pmd_free((tlb)->mm, (pmdp));                    \
> > >  } while (0);
> > >  #endif
>
> OK, so I was going to write a Changelog to go with that, but then I
> realized that while this works and is similar to before the patch, I'm
> not sure this is in fact correct.
>
> With this on (and also before) we're freeing the PMD before we've done
> the TLB invalidate, that seems wrong!
>
> Looking at the size of that pmd_cache, that looks to be 30-(12+12-3)+3
> == 12, which is exactly 1 page, for PAGE_SIZE_4K, less for the larger
> pages.
>
> I'm thinking perhaps we should do something like the below instead?

Your advice is better when in close vicinity of an SH cross compiler,
though ;-)

> --- a/arch/sh/mm/pgtable.c
> +++ b/arch/sh/mm/pgtable.c
> @@ -5,9 +5,6 @@
>  #define PGALLOC_GFP GFP_KERNEL | __GFP_ZERO
>
>  static struct kmem_cache *pgd_cachep;
> -#if PAGETABLE_LEVELS > 2
> -static struct kmem_cache *pmd_cachep;
> -#endif
>
>  void pgd_ctor(void *x)
>  {
> @@ -23,11 +20,6 @@ void pgtable_cache_init(void)
>         pgd_cachep = kmem_cache_create("pgd_cache",
>                                        PTRS_PER_PGD * (1<<PTE_MAGNITUDE),
>                                        PAGE_SIZE, SLAB_PANIC, pgd_ctor);
> -#if PAGETABLE_LEVELS > 2
> -       pmd_cachep = kmem_cache_create("pmd_cache",
> -                                      PTRS_PER_PMD * (1<<PTE_MAGNITUDE),
> -                                      PAGE_SIZE, SLAB_PANIC, NULL);
> -#endif
>  }
>
>  pgd_t *pgd_alloc(struct mm_struct *mm)
> @@ -48,11 +40,7 @@ void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
>
>  pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
>  {
> -       return kmem_cache_alloc(pmd_cachep, PGALLOC_GFP);
> -}
> -
> -void pmd_free(struct mm_struct *mm, pmd_t *pmd)

mm/memory.o: In function `__pmd_alloc':
memory.c:(.text+0x1d74): undefined reference to `pmd_free'

> -{
> -       kmem_cache_free(pmd_cachep, pmd);
> +       BUILD_BUG_ON(PTRS_PER_PMD * (1<<PTE_MAGNITUDE) <= PAGE_SIZE);

... > PAGE_SIZE ?

Else it triggers all the time.

> +       return (pmd_t *)__get_free_page(PGALLOC_GFP);
>  }
>  #endif /* PAGETABLE_LEVELS > 2 */

BTW, I'm still running Willy's fix that never made it upstream
to kill an ugly boot warning, which also touches this code:
https://patchwork.kernel.org/patch/10549883/#22166333

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds


  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-19 10:31 [PATCH v6 00/18] generic mmu_gather patches Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 01/18] asm-generic/tlb: Provide a comment Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 02/18] asm-generic/tlb: Provide HAVE_MMU_GATHER_PAGE_SIZE Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 03/18] asm-generic/tlb: Provide generic VIPT cache flush Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 04/18] asm-generic/tlb: Provide generic tlb_flush() based on flush_tlb_range() Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 05/18] asm-generic/tlb: Provide generic tlb_flush() based on flush_tlb_mm() Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:31 ` [PATCH v6 06/18] asm-generic/tlb: Conditionally provide tlb_migrate_finish() Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 13:41     ` Peter Zijlstra
2019-02-20 14:47       ` Will Deacon
2019-02-20 15:02         ` Matthew Wilcox
2019-02-19 10:31 ` [PATCH v6 07/18] asm-generic/tlb: Invert HAVE_RCU_TABLE_INVALIDATE Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 08/18] arm/tlb: Convert to generic mmu_gather Peter Zijlstra
2019-02-19 10:31 ` [PATCH v6 09/18] ia64/tlb: Conver " Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-21  2:52   ` Souptick Joarder
2019-02-19 10:31 ` [PATCH v6 10/18] sh/tlb: Convert SH " Peter Zijlstra
2019-12-03 11:19   ` Geert Uytterhoeven
2019-12-04 10:47     ` Peter Zijlstra
2019-12-04 12:32       ` Geert Uytterhoeven
2019-12-04 13:22         ` Guenter Roeck
2019-12-04 15:17           ` Geert Uytterhoeven
2019-12-04 19:03             ` Guenter Roeck
2019-12-04 13:34         ` Peter Zijlstra
2019-12-04 15:07           ` Geert Uytterhoeven
2019-12-04 16:41             ` Peter Zijlstra
2019-12-05 15:26               ` Geert Uytterhoeven [this message]
2019-12-05 19:24       ` Rob Landley
2019-12-05 19:23         ` Rich Felker
2019-12-05 19:30       ` John Paul Adrian Glaubitz
2019-12-05 22:56         ` Guenter Roeck
2019-12-06 13:38           ` John Paul Adrian Glaubitz
2019-12-06 14:03             ` Guenter Roeck
2019-02-19 10:31 ` [PATCH v6 11/18] um/tlb: Convert " Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 12/18] arch/tlb: Clean up simple architectures Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 13/18] asm-generic/tlb: Introduce HAVE_MMU_GATHER_NO_GATHER Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:32 ` [PATCH v6 14/18] s390/tlb: convert to generic mmu_gather Peter Zijlstra
2019-02-19 12:47   ` Will Deacon
2019-02-19 10:32 ` [PATCH v6 15/18] asm-generic/tlb: Remove arch_tlb*_mmu() Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 16/18] asm-generic/tlb: Remove HAVE_GENERIC_MMU_GATHER Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 17/18] asm-generic/tlb: Remove tlb_flush_mmu_free() Peter Zijlstra
2019-02-19 10:32 ` [PATCH v6 18/18] asm-generic/tlb: Remove tlb_table_flush() Peter Zijlstra

Reply instructions:

You may reply publically 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=CAMuHMdVQO6vMDuns7rwk8sD+cPhEVQjEU_DiKiTQn0NY2ppzag@mail.gmail.com \
    --to=geert@linux-m68k.org \
    --cc=akpm@linux-foundation.org \
    --cc=aneesh.kumar@linux.vnet.ibm.com \
    --cc=dalias@libc.org \
    --cc=heiko.carstens@de.ibm.com \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-sh@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    --cc=linux@roeck-us.net \
    --cc=npiggin@gmail.com \
    --cc=peterz@infradead.org \
    --cc=riel@surriel.com \
    --cc=will.deacon@arm.com \
    --cc=ysato@users.sourceforge.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git