From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/2] arm64: mem-model: add flatmem model for arm64
Date: Mon, 11 Apr 2016 11:40:13 +0100 [thread overview]
Message-ID: <20160411104013.GG15729@arm.com> (raw)
In-Reply-To: <CAKv+Gu-cWWUi6fCiveqaZRVhGCpEasCLEs7wq6t+C-x65g4cgQ@mail.gmail.com>
On Mon, Apr 11, 2016 at 12:31:53PM +0200, Ard Biesheuvel wrote:
> On 11 April 2016 at 11:59, Chen Feng <puck.chen@hisilicon.com> wrote:
> > Please see the pg-tables below.
> >
> >
> > With sparse and vmemmap enable.
> >
> > ---[ vmemmap start ]---
> > 0xffffffbdc0200000-0xffffffbdc4800000 70M RW NX SHD AF UXN MEM/NORMAL
> > ---[ vmemmap end ]---
> >
>
> OK, I see what you mean now. Sorry for taking so long to catch up.
>
> > The board is 4GB, and the memap is 70MB
> > 1G memory --- 14MB mem_map array.
>
> No, this is incorrect. 1 GB corresponds with 16 MB worth of struct
> pages assuming sizeof(struct page) == 64
>
> So you are losing 6 MB to rounding here, which I agree is significant.
> I wonder if it makes sense to use a lower value for SECTION_SIZE_BITS
> on 4k pages kernels, but perhaps we're better off asking the opinion
> of the other cc'ees.
You need to be really careful making SECTION_SIZE_BITS smaller because
it has a direct correlation on the use of page->flags and you can end up
running out of bits fairly easily.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Chen Feng <puck.chen@hisilicon.com>,
Mark Rutland <mark.rutland@arm.com>,
mhocko@suse.com, Laura Abbott <labbott@redhat.com>,
Dan Zhao <dan.zhao@hisilicon.com>,
Yiping Xu <xuyiping@hisilicon.com>,
puck.chen@foxmail.com, albert.lubing@hisilicon.com,
Catalin Marinas <catalin.marinas@arm.com>,
suzhuangluan@hisilicon.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linuxarm@huawei.com, "linux-mm@kvack.org" <linux-mm@kvack.org>,
kirill.shutemov@linux.intel.com,
David Rientjes <rientjes@google.com>,
oliver.fu@hisilicon.com,
Andrew Morton <akpm@linux-foundation.org>,
robin.murphy@arm.com,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
saberlily.xia@hisilicon.com
Subject: Re: [PATCH 1/2] arm64: mem-model: add flatmem model for arm64
Date: Mon, 11 Apr 2016 11:40:13 +0100 [thread overview]
Message-ID: <20160411104013.GG15729@arm.com> (raw)
In-Reply-To: <CAKv+Gu-cWWUi6fCiveqaZRVhGCpEasCLEs7wq6t+C-x65g4cgQ@mail.gmail.com>
On Mon, Apr 11, 2016 at 12:31:53PM +0200, Ard Biesheuvel wrote:
> On 11 April 2016 at 11:59, Chen Feng <puck.chen@hisilicon.com> wrote:
> > Please see the pg-tables below.
> >
> >
> > With sparse and vmemmap enable.
> >
> > ---[ vmemmap start ]---
> > 0xffffffbdc0200000-0xffffffbdc4800000 70M RW NX SHD AF UXN MEM/NORMAL
> > ---[ vmemmap end ]---
> >
>
> OK, I see what you mean now. Sorry for taking so long to catch up.
>
> > The board is 4GB, and the memap is 70MB
> > 1G memory --- 14MB mem_map array.
>
> No, this is incorrect. 1 GB corresponds with 16 MB worth of struct
> pages assuming sizeof(struct page) == 64
>
> So you are losing 6 MB to rounding here, which I agree is significant.
> I wonder if it makes sense to use a lower value for SECTION_SIZE_BITS
> on 4k pages kernels, but perhaps we're better off asking the opinion
> of the other cc'ees.
You need to be really careful making SECTION_SIZE_BITS smaller because
it has a direct correlation on the use of page->flags and you can end up
running out of bits fairly easily.
Will
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WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Chen Feng <puck.chen@hisilicon.com>,
Mark Rutland <mark.rutland@arm.com>,
mhocko@suse.com, Laura Abbott <labbott@redhat.com>,
Dan Zhao <dan.zhao@hisilicon.com>,
Yiping Xu <xuyiping@hisilicon.com>,
puck.chen@foxmail.com, albert.lubing@hisilicon.com,
Catalin Marinas <catalin.marinas@arm.com>,
suzhuangluan@hisilicon.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linuxarm@huawei.com, "linux-mm@kvack.org" <linux-mm@kvack.org>,
kirill.shutemov@linux.intel.com,
David Rientjes <rientjes@google.com>,
oliver.fu@hisilicon.com,
Andrew Morton <akpm@linux-foundation.org>,
robin.murphy@arm.com,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
saberlily.xia@hisilicon.com
Subject: Re: [PATCH 1/2] arm64: mem-model: add flatmem model for arm64
Date: Mon, 11 Apr 2016 11:40:13 +0100 [thread overview]
Message-ID: <20160411104013.GG15729@arm.com> (raw)
In-Reply-To: <CAKv+Gu-cWWUi6fCiveqaZRVhGCpEasCLEs7wq6t+C-x65g4cgQ@mail.gmail.com>
On Mon, Apr 11, 2016 at 12:31:53PM +0200, Ard Biesheuvel wrote:
> On 11 April 2016 at 11:59, Chen Feng <puck.chen@hisilicon.com> wrote:
> > Please see the pg-tables below.
> >
> >
> > With sparse and vmemmap enable.
> >
> > ---[ vmemmap start ]---
> > 0xffffffbdc0200000-0xffffffbdc4800000 70M RW NX SHD AF UXN MEM/NORMAL
> > ---[ vmemmap end ]---
> >
>
> OK, I see what you mean now. Sorry for taking so long to catch up.
>
> > The board is 4GB, and the memap is 70MB
> > 1G memory --- 14MB mem_map array.
>
> No, this is incorrect. 1 GB corresponds with 16 MB worth of struct
> pages assuming sizeof(struct page) == 64
>
> So you are losing 6 MB to rounding here, which I agree is significant.
> I wonder if it makes sense to use a lower value for SECTION_SIZE_BITS
> on 4k pages kernels, but perhaps we're better off asking the opinion
> of the other cc'ees.
You need to be really careful making SECTION_SIZE_BITS smaller because
it has a direct correlation on the use of page->flags and you can end up
running out of bits fairly easily.
Will
next prev parent reply other threads:[~2016-04-11 10:40 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-05 8:22 [PATCH 1/2] arm64: mem-model: add flatmem model for arm64 Chen Feng
2016-04-05 8:22 ` Chen Feng
2016-04-05 8:22 ` Chen Feng
2016-04-05 8:22 ` [PATCH 2/2] arm64: mm: make pfn always valid with flat memory Chen Feng
2016-04-05 8:22 ` Chen Feng
2016-04-05 8:22 ` Chen Feng
2016-04-07 7:39 ` Chen Feng
2016-04-07 7:39 ` Chen Feng
2016-04-07 7:39 ` Chen Feng
2016-04-11 11:08 ` Xishi Qiu
2016-04-11 11:08 ` Xishi Qiu
2016-04-11 11:08 ` Xishi Qiu
2016-04-12 15:00 ` Catalin Marinas
2016-04-12 15:00 ` Catalin Marinas
2016-04-12 15:00 ` Catalin Marinas
2016-04-07 7:38 ` [PATCH 1/2] arm64: mem-model: add flatmem model for arm64 Chen Feng
2016-04-07 7:38 ` Chen Feng
2016-04-07 7:38 ` Chen Feng
2016-04-07 14:21 ` Will Deacon
2016-04-07 14:21 ` Will Deacon
2016-04-07 14:21 ` Will Deacon
2016-04-11 2:49 ` Chen Feng
2016-04-11 2:49 ` Chen Feng
2016-04-11 2:49 ` Chen Feng
2016-04-11 7:35 ` Ard Biesheuvel
2016-04-11 7:35 ` Ard Biesheuvel
2016-04-11 7:35 ` Ard Biesheuvel
2016-04-11 7:55 ` Chen Feng
2016-04-11 7:55 ` Chen Feng
2016-04-11 7:55 ` Chen Feng
2016-04-11 8:00 ` Ard Biesheuvel
2016-04-11 8:00 ` Ard Biesheuvel
2016-04-11 8:00 ` Ard Biesheuvel
2016-04-11 9:59 ` Chen Feng
2016-04-11 9:59 ` Chen Feng
2016-04-11 9:59 ` Chen Feng
2016-04-11 10:31 ` Ard Biesheuvel
2016-04-11 10:31 ` Ard Biesheuvel
2016-04-11 10:31 ` Ard Biesheuvel
2016-04-11 10:40 ` Will Deacon [this message]
2016-04-11 10:40 ` Will Deacon
2016-04-11 10:40 ` Will Deacon
2016-04-11 10:57 ` Chen Feng
2016-04-11 10:57 ` Chen Feng
2016-04-11 10:57 ` Chen Feng
2016-04-11 18:11 ` Laura Abbott
2016-04-11 18:11 ` Laura Abbott
2016-04-11 18:11 ` Laura Abbott
2016-04-12 14:44 ` Catalin Marinas
2016-04-12 14:44 ` Catalin Marinas
2016-04-12 14:44 ` Catalin Marinas
2016-04-12 14:59 ` Catalin Marinas
2016-04-12 14:59 ` Catalin Marinas
2016-04-12 14:59 ` Catalin Marinas
2016-04-20 3:18 ` Chen Feng
2016-04-20 3:18 ` Chen Feng
2016-04-20 3:18 ` Chen Feng
2016-04-20 9:32 ` Catalin Marinas
2016-04-20 9:32 ` Catalin Marinas
2016-04-20 9:32 ` Catalin Marinas
2016-04-11 10:48 ` Chen Feng
2016-04-11 10:48 ` Chen Feng
2016-04-11 10:48 ` Chen Feng
2016-04-11 11:02 ` Ard Biesheuvel
2016-04-11 11:02 ` Ard Biesheuvel
2016-04-11 11:02 ` Ard Biesheuvel
2016-04-12 14:03 ` Jungseok Lee
2016-04-12 14:03 ` Jungseok Lee
2016-04-12 14:03 ` Jungseok Lee
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