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From: Robert Richter <robert.richter@cavium.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Will Deacon <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hanjun Guo <hanjun.guo@linaro.org>,
	Yisheng Xie <xieyisheng1@huawei.com>,
	James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Fri, 16 Dec 2016 18:10:16 +0100	[thread overview]
Message-ID: <20161216170947.GD4930@rric.localdomain> (raw)
In-Reply-To: <CAKv+Gu8K+mokbjzM8EpTJoCp3XAKK1_Doq1Zx=A2CCWTT6FbYg@mail.gmail.com>

On 15.12.16 16:07:26, Ard Biesheuvel wrote:
> On 15 December 2016 at 15:39, Robert Richter <robert.richter@cavium.com> wrote:
> > I was going to do some measurements but my kernel crashes now with a
> > page fault in efi_rtc_probe():
> >
> > [   21.663393] Unable to handle kernel paging request at virtual address 20251000
> > [   21.663396] pgd = ffff000009090000
> > [   21.663401] [20251000] *pgd=0000010ffff90003
> > [   21.663402] , *pud=0000010ffff90003
> > [   21.663404] , *pmd=0000000fdc030003
> > [   21.663405] , *pte=00e8832000250707
> >
> > The sparsemem config requires the whole section to be initialized.
> > Your patches do not address this.
> >
> 
> 96000047 is a third level translation fault, and the PTE address has
> RES0 bits set. I don't see how this is related to sparsemem, could you
> explain?

When initializing the whole section it works. Maybe it uncovers
another bug. Did not yet start debugging this.

> 
> > On 14.12.16 09:11:47, Ard Biesheuvel wrote:
> >> +config HOLES_IN_ZONE
> >> +     def_bool y
> >> +     depends on NUMA
> >
> > This enables pfn_valid_within() for arm64 and causes the check for
> > each page of a section. The arm64 implementation of pfn_valid() is
> > already expensive (traversing memblock areas). Now, this is increased
> > by a factor of 2^18 for 4k page size (16384 for 64k). We need to
> > initialize the whole section to avoid that.
> >
> 
> I know that. But if you want something for -stable, we should have
> something that is correct first, and only then care about the
> performance hit (if there is one)

I would prefer to check for a performance penalty *before* we put it
into stable. There is nor risk at all with the patch I am proposing.
See: https://lkml.org/lkml/2016/12/16/412

-Robert

WARNING: multiple messages have this Message-ID (diff)
From: Robert Richter <robert.richter@cavium.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Will Deacon <will.deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hanjun Guo <hanjun.guo@linaro.org>,
	Yisheng Xie <xieyisheng1@huawei.com>,
	James Morse <james.morse@arm.com>
Subject: Re: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Fri, 16 Dec 2016 18:10:16 +0100	[thread overview]
Message-ID: <20161216170947.GD4930@rric.localdomain> (raw)
In-Reply-To: <CAKv+Gu8K+mokbjzM8EpTJoCp3XAKK1_Doq1Zx=A2CCWTT6FbYg@mail.gmail.com>

On 15.12.16 16:07:26, Ard Biesheuvel wrote:
> On 15 December 2016 at 15:39, Robert Richter <robert.richter@cavium.com> wrote:
> > I was going to do some measurements but my kernel crashes now with a
> > page fault in efi_rtc_probe():
> >
> > [   21.663393] Unable to handle kernel paging request at virtual address 20251000
> > [   21.663396] pgd = ffff000009090000
> > [   21.663401] [20251000] *pgd=0000010ffff90003
> > [   21.663402] , *pud=0000010ffff90003
> > [   21.663404] , *pmd=0000000fdc030003
> > [   21.663405] , *pte=00e8832000250707
> >
> > The sparsemem config requires the whole section to be initialized.
> > Your patches do not address this.
> >
> 
> 96000047 is a third level translation fault, and the PTE address has
> RES0 bits set. I don't see how this is related to sparsemem, could you
> explain?

When initializing the whole section it works. Maybe it uncovers
another bug. Did not yet start debugging this.

> 
> > On 14.12.16 09:11:47, Ard Biesheuvel wrote:
> >> +config HOLES_IN_ZONE
> >> +     def_bool y
> >> +     depends on NUMA
> >
> > This enables pfn_valid_within() for arm64 and causes the check for
> > each page of a section. The arm64 implementation of pfn_valid() is
> > already expensive (traversing memblock areas). Now, this is increased
> > by a factor of 2^18 for 4k page size (16384 for 64k). We need to
> > initialize the whole section to avoid that.
> >
> 
> I know that. But if you want something for -stable, we should have
> something that is correct first, and only then care about the
> performance hit (if there is one)

I would prefer to check for a performance penalty *before* we put it
into stable. There is nor risk at all with the patch I am proposing.
See: https://lkml.org/lkml/2016/12/16/412

-Robert

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WARNING: multiple messages have this Message-ID (diff)
From: robert.richter@cavium.com (Robert Richter)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA
Date: Fri, 16 Dec 2016 18:10:16 +0100	[thread overview]
Message-ID: <20161216170947.GD4930@rric.localdomain> (raw)
In-Reply-To: <CAKv+Gu8K+mokbjzM8EpTJoCp3XAKK1_Doq1Zx=A2CCWTT6FbYg@mail.gmail.com>

On 15.12.16 16:07:26, Ard Biesheuvel wrote:
> On 15 December 2016 at 15:39, Robert Richter <robert.richter@cavium.com> wrote:
> > I was going to do some measurements but my kernel crashes now with a
> > page fault in efi_rtc_probe():
> >
> > [   21.663393] Unable to handle kernel paging request at virtual address 20251000
> > [   21.663396] pgd = ffff000009090000
> > [   21.663401] [20251000] *pgd=0000010ffff90003
> > [   21.663402] , *pud=0000010ffff90003
> > [   21.663404] , *pmd=0000000fdc030003
> > [   21.663405] , *pte=00e8832000250707
> >
> > The sparsemem config requires the whole section to be initialized.
> > Your patches do not address this.
> >
> 
> 96000047 is a third level translation fault, and the PTE address has
> RES0 bits set. I don't see how this is related to sparsemem, could you
> explain?

When initializing the whole section it works. Maybe it uncovers
another bug. Did not yet start debugging this.

> 
> > On 14.12.16 09:11:47, Ard Biesheuvel wrote:
> >> +config HOLES_IN_ZONE
> >> +     def_bool y
> >> +     depends on NUMA
> >
> > This enables pfn_valid_within() for arm64 and causes the check for
> > each page of a section. The arm64 implementation of pfn_valid() is
> > already expensive (traversing memblock areas). Now, this is increased
> > by a factor of 2^18 for 4k page size (16384 for 64k). We need to
> > initialize the whole section to avoid that.
> >
> 
> I know that. But if you want something for -stable, we should have
> something that is correct first, and only then care about the
> performance hit (if there is one)

I would prefer to check for a performance penalty *before* we put it
into stable. There is nor risk at all with the patch I am proposing.
See: https://lkml.org/lkml/2016/12/16/412

-Robert

  reply	other threads:[~2016-12-16 17:10 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-14  9:11 [PATCH 0/2] arm64: numa: fix spurious BUG() on NOMAP regions Ard Biesheuvel
2016-12-14  9:11 ` Ard Biesheuvel
2016-12-14  9:11 ` Ard Biesheuvel
2016-12-14  9:11 ` [PATCH 1/2] mm: don't dereference struct page fields of invalid pages Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2017-01-04 12:16   ` Will Deacon
2017-01-04 12:16     ` Will Deacon
2017-01-04 12:16     ` Will Deacon
2016-12-14  9:11 ` [PATCH 2/2] arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-14  9:11   ` Ard Biesheuvel
2016-12-15 15:39   ` Robert Richter
2016-12-15 15:39     ` Robert Richter
2016-12-15 15:39     ` Robert Richter
2016-12-15 16:07     ` Ard Biesheuvel
2016-12-15 16:07       ` Ard Biesheuvel
2016-12-15 16:07       ` Ard Biesheuvel
2016-12-16 17:10       ` Robert Richter [this message]
2016-12-16 17:10         ` Robert Richter
2016-12-16 17:10         ` Robert Richter
2016-12-16  1:57     ` Hanjun Guo
2016-12-16  1:57       ` Hanjun Guo
2016-12-16  1:57       ` Hanjun Guo
2016-12-16 17:14       ` Robert Richter
2016-12-16 17:14         ` Robert Richter
2016-12-16 17:14         ` Robert Richter
2017-01-04 13:28   ` Will Deacon
2017-01-04 13:28     ` Will Deacon
2017-01-04 13:28     ` Will Deacon
2017-01-04 13:50     ` Ard Biesheuvel
2017-01-04 13:50       ` Ard Biesheuvel
2017-01-04 13:50       ` Ard Biesheuvel
2017-01-04 14:02       ` Will Deacon
2017-01-04 14:02         ` Will Deacon
2017-01-04 14:02         ` Will Deacon
2017-01-05 11:24         ` Robert Richter
2017-01-05 11:24           ` Robert Richter
2017-01-05 11:24           ` Robert Richter
2017-01-05 12:08           ` Will Deacon
2017-01-05 12:08             ` Will Deacon
2017-01-05 12:08             ` Will Deacon
2017-01-05 12:22             ` Robert Richter
2017-01-05 12:22               ` Robert Richter
2017-01-05 12:22               ` Robert Richter
2017-01-05 19:49               ` Robert Richter
2017-01-05 19:49                 ` Robert Richter
2017-01-05 19:49                 ` Robert Richter
2017-01-06 12:03                 ` Will Deacon
2017-01-06 12:03                   ` Will Deacon
2017-01-06 12:03                   ` Will Deacon
2017-01-06 12:22                   ` Ard Biesheuvel
2017-01-06 12:22                     ` Ard Biesheuvel
2017-01-06 12:22                     ` Ard Biesheuvel
2017-02-06 13:36   ` Robert Richter
2017-02-06 13:36     ` Robert Richter
2017-02-06 13:36     ` Robert Richter

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