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From: Joerg Roedel <jroedel@suse.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: Joerg Roedel <joro@8bytes.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range()
Date: Thu, 18 Jul 2019 11:17:45 +0200	[thread overview]
Message-ID: <20190718091745.GG13091@suse.de> (raw)
In-Reply-To: <CALCETrXfCbajLhUixKNaMfFw91gzoQzt__faYLwyBqA3eAbQVA@mail.gmail.com>

Hi Andy,

On Wed, Jul 17, 2019 at 02:24:09PM -0700, Andy Lutomirski wrote:
> On Wed, Jul 17, 2019 at 12:14 AM Joerg Roedel <joro@8bytes.org> wrote:
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 4fa8d84599b0..322b11a374fd 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -132,6 +132,8 @@ static void vunmap_page_range(unsigned long addr, unsigned long end)
> >                         continue;
> >                 vunmap_p4d_range(pgd, addr, next);
> >         } while (pgd++, addr = next, addr != end);
> > +
> > +       vmalloc_sync_all();
> >  }
> 
> I'm confused.  Shouldn't the code in _vm_unmap_aliases handle this?
> As it stands, won't your patch hurt performance on x86_64?  If x86_32
> is a special snowflake here, maybe flush_tlb_kernel_range() should
> handle this?

Imo this is the logical place to handle this. The code first unmaps the
area from the init_mm page-table and then syncs that page-table to all
other page-tables in the system, so one place to update the page-tables.

Performance-wise it makes no difference if we put that into
_vm_unmap_aliases(), as that is called in the vmunmap path too. But it
is right that vmunmap/iounmap performance on x86-64 will decrease to
some degree. If that is a problem for some workloads I can also
implement a complete separate code-path which just syncs unmappings and
is only implemented for x86-32 with !SHARED_KERNEL_PMD.

Regards,

	Joerg

  reply	other threads:[~2019-07-18  9:17 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17  7:14 [PATCH 0/3 v2] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-17  7:14 ` [PATCH 1/3] x86/mm: Check for pfn instead of page in vmalloc_sync_one() Joerg Roedel
2019-07-17  7:14 ` [PATCH 2/3] x86/mm: Sync also unmappings " Joerg Roedel
2019-07-17 21:06   ` Dave Hansen
2019-07-18  8:44     ` Joerg Roedel
2019-07-17 21:43   ` Thomas Gleixner
2019-07-18  8:46     ` Joerg Roedel
2019-07-18  9:04       ` Thomas Gleixner
2019-07-18  9:25         ` Joerg Roedel
2019-07-19 14:01         ` Joerg Roedel
2019-07-19 21:10           ` Thomas Gleixner
2019-07-17  7:14 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
2019-07-17 21:24   ` Andy Lutomirski
2019-07-18  9:17     ` Joerg Roedel [this message]
2019-07-18 19:04       ` Andy Lutomirski
2019-07-19 12:21         ` Joerg Roedel
2019-07-19 12:24           ` Andy Lutomirski
2019-07-19 13:00             ` Joerg Roedel
  -- strict thread matches above, loose matches on Subject: below --
2019-07-19 18:46 [PATCH 0/3 v3] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-19 18:46 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel
2019-07-22  8:11   ` Joerg Roedel
2019-07-22  8:19     ` Thomas Gleixner
2019-07-22  8:29       ` Joerg Roedel
2019-07-15 11:02 [PATCH 0/3] Sync unmappings in vmalloc/ioremap areas Joerg Roedel
2019-07-15 11:02 ` [PATCH 3/3] mm/vmalloc: Sync unmappings in vunmap_page_range() Joerg Roedel

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