From: Arnd Bergmann <arnd@arndb.de>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>,
Albert Ou <aou@eecs.berkeley.edu>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Linux-MM <linux-mm@kvack.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Anup Patel <Anup.Patel@wdc.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Atish Patra <Atish.Patra@wdc.com>,
Paul Mackerras <paulus@samba.org>, Zong Li <zong.li@sifive.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
linux-riscv <linux-riscv@lists.infradead.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone
Date: Wed, 22 Jul 2020 22:22:25 +0200 [thread overview]
Message-ID: <CAK8P3a2VHXDLK6iba=NxSQ-t=9P7LSwzwx3XrK=N=M+qoX_oeQ@mail.gmail.com> (raw)
In-Reply-To: <mhng-820ebe55-b4a3-4ab3-b848-6d3551b43091@palmerdabbelt-glaptop1>
On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote:
> > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > The eventual goal is to have a split of 3840MB for either user or linear map
> > plus and 256MB for vmalloc, including the kernel. Switching between linear
> > and user has a noticeable runtime overhead, but it relaxes both the limits
> > for user memory and lowmem, and it provides a somewhat stronger
> > address space isolation.
>
> Ya, I think we decided not to do that, at least for now. I guess the right
> answer there will depend on what 32-bit systems look like, and since we don't
> have any I'm inclined to just stick to the fast option.
Makes sense. Actually on 32-bit Arm we see fewer large-memory
configurations in new machines than we had in the past before 64-bit
machines were widely available at low cost, so I expect not to see a
lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips)
for cost reasons, and rv32 is likely going to be similar, so you may never
really see a need for highmem or the above hack to increase the
size of the linear mapping.
I just noticed that rv32 allows 2GB of lowmem rather than just the usual
768MB or 1GB, at the expense of addressable user memory. This seems
like an unusual choice, but I also don't see any reason to change this
or make it more flexible unless actual users appear.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Atish Patra <Atish.Patra@wdc.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Anup Patel <Anup.Patel@wdc.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Linux-MM <linux-mm@kvack.org>, Paul Mackerras <paulus@samba.org>,
Zong Li <zong.li@sifive.com>,
Michael Ellerman <mpe@ellerman.id.au>,
linux-riscv <linux-riscv@lists.infradead.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone
Date: Wed, 22 Jul 2020 22:22:25 +0200 [thread overview]
Message-ID: <CAK8P3a2VHXDLK6iba=NxSQ-t=9P7LSwzwx3XrK=N=M+qoX_oeQ@mail.gmail.com> (raw)
In-Reply-To: <mhng-820ebe55-b4a3-4ab3-b848-6d3551b43091@palmerdabbelt-glaptop1>
On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote:
> > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > The eventual goal is to have a split of 3840MB for either user or linear map
> > plus and 256MB for vmalloc, including the kernel. Switching between linear
> > and user has a noticeable runtime overhead, but it relaxes both the limits
> > for user memory and lowmem, and it provides a somewhat stronger
> > address space isolation.
>
> Ya, I think we decided not to do that, at least for now. I guess the right
> answer there will depend on what 32-bit systems look like, and since we don't
> have any I'm inclined to just stick to the fast option.
Makes sense. Actually on 32-bit Arm we see fewer large-memory
configurations in new machines than we had in the past before 64-bit
machines were widely available at low cost, so I expect not to see a
lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips)
for cost reasons, and rv32 is likely going to be similar, so you may never
really see a need for highmem or the above hack to increase the
size of the linear mapping.
I just noticed that rv32 allows 2GB of lowmem rather than just the usual
768MB or 1GB, at the expense of addressable user memory. This seems
like an unusual choice, but I also don't see any reason to change this
or make it more flexible unless actual users appear.
Arnd
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linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>,
Atish Patra <Atish.Patra@wdc.com>,
Anup Patel <Anup.Patel@wdc.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Linux-MM <linux-mm@kvack.org>, Paul Mackerras <paulus@samba.org>,
Zong Li <zong.li@sifive.com>,
linux-riscv <linux-riscv@lists.infradead.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone
Date: Wed, 22 Jul 2020 22:22:25 +0200 [thread overview]
Message-ID: <CAK8P3a2VHXDLK6iba=NxSQ-t=9P7LSwzwx3XrK=N=M+qoX_oeQ@mail.gmail.com> (raw)
In-Reply-To: <mhng-820ebe55-b4a3-4ab3-b848-6d3551b43091@palmerdabbelt-glaptop1>
On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote:
> > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt <palmer@dabbelt.com> wrote:
> > The eventual goal is to have a split of 3840MB for either user or linear map
> > plus and 256MB for vmalloc, including the kernel. Switching between linear
> > and user has a noticeable runtime overhead, but it relaxes both the limits
> > for user memory and lowmem, and it provides a somewhat stronger
> > address space isolation.
>
> Ya, I think we decided not to do that, at least for now. I guess the right
> answer there will depend on what 32-bit systems look like, and since we don't
> have any I'm inclined to just stick to the fast option.
Makes sense. Actually on 32-bit Arm we see fewer large-memory
configurations in new machines than we had in the past before 64-bit
machines were widely available at low cost, so I expect not to see a
lot new hardware with more than 1GB of DDR3 (two 256Mbit x16 chips)
for cost reasons, and rv32 is likely going to be similar, so you may never
really see a need for highmem or the above hack to increase the
size of the linear mapping.
I just noticed that rv32 allows 2GB of lowmem rather than just the usual
768MB or 1GB, at the expense of addressable user memory. This seems
like an unusual choice, but I also don't see any reason to change this
or make it more flexible unless actual users appear.
Arnd
next prev parent reply other threads:[~2020-07-22 20:22 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-07 7:59 [PATCH v5 0/4] vmalloc kernel mapping and relocatable kernel Alexandre Ghiti
2020-06-07 7:59 ` [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone Alexandre Ghiti
2020-06-11 21:34 ` Atish Patra
2020-06-11 21:34 ` Atish Patra
2020-06-11 21:34 ` Atish Patra
2020-06-12 12:30 ` Alex Ghiti
2020-06-12 12:30 ` Alex Ghiti
2020-06-12 12:30 ` Alex Ghiti
2020-07-09 5:05 ` Palmer Dabbelt
2020-07-09 5:05 ` Palmer Dabbelt
2020-07-09 5:05 ` Palmer Dabbelt
2020-07-09 8:15 ` Zong Li
2020-07-09 8:15 ` Zong Li
2020-07-09 8:15 ` Zong Li
2020-07-09 11:11 ` Alex Ghiti
2020-07-09 11:11 ` Alex Ghiti
2020-07-09 11:11 ` Alex Ghiti
2020-07-21 18:36 ` Alex Ghiti
2020-07-21 18:36 ` Alex Ghiti
2020-07-21 18:36 ` Alex Ghiti
2020-07-21 19:05 ` Palmer Dabbelt
2020-07-21 19:05 ` Palmer Dabbelt
2020-07-21 19:05 ` Palmer Dabbelt
2020-07-21 23:12 ` Benjamin Herrenschmidt
2020-07-21 23:12 ` Benjamin Herrenschmidt
2020-07-21 23:12 ` Benjamin Herrenschmidt
2020-07-21 23:48 ` Palmer Dabbelt
2020-07-21 23:48 ` Palmer Dabbelt
2020-07-21 23:48 ` Palmer Dabbelt
2020-07-22 2:21 ` Benjamin Herrenschmidt
2020-07-22 2:21 ` Benjamin Herrenschmidt
2020-07-22 2:21 ` Benjamin Herrenschmidt
2020-07-22 4:50 ` Michael Ellerman
2020-07-22 4:50 ` Michael Ellerman
2020-07-22 4:50 ` Michael Ellerman
2020-07-22 5:46 ` Palmer Dabbelt
2020-07-22 5:46 ` Palmer Dabbelt
2020-07-22 5:46 ` Palmer Dabbelt
2020-07-22 9:43 ` Arnd Bergmann
2020-07-22 9:43 ` Arnd Bergmann
2020-07-22 9:43 ` Arnd Bergmann
2020-07-22 9:43 ` Arnd Bergmann
2020-07-22 19:52 ` Palmer Dabbelt
2020-07-22 19:52 ` Palmer Dabbelt
2020-07-22 19:52 ` Palmer Dabbelt
2020-07-22 20:22 ` Arnd Bergmann [this message]
2020-07-22 20:22 ` Arnd Bergmann
2020-07-22 20:22 ` Arnd Bergmann
2020-07-22 20:22 ` Arnd Bergmann
2020-07-22 21:05 ` Atish Patra
2020-07-22 21:05 ` Atish Patra
2020-07-22 21:05 ` Atish Patra
2020-07-22 21:05 ` Atish Patra
2020-07-24 7:20 ` Arnd Bergmann
2020-07-24 7:20 ` Arnd Bergmann
2020-07-24 7:20 ` Arnd Bergmann
2020-07-24 7:20 ` Arnd Bergmann
2020-07-23 5:32 ` Alex Ghiti
2020-07-23 5:32 ` Alex Ghiti
2020-07-23 5:32 ` Alex Ghiti
2020-07-21 23:11 ` Benjamin Herrenschmidt
2020-07-21 23:11 ` Benjamin Herrenschmidt
2020-07-21 23:11 ` Benjamin Herrenschmidt
2020-07-21 23:36 ` Palmer Dabbelt
2020-07-21 23:36 ` Palmer Dabbelt
2020-07-21 23:36 ` Palmer Dabbelt
2020-07-23 5:36 ` Alex Ghiti
2020-07-23 5:36 ` Alex Ghiti
2020-07-23 5:36 ` Alex Ghiti
2020-07-23 5:21 ` Alex Ghiti
2020-07-23 5:21 ` Alex Ghiti
2020-07-23 5:21 ` Alex Ghiti
2020-07-23 22:33 ` Benjamin Herrenschmidt
2020-07-23 22:33 ` Benjamin Herrenschmidt
2020-07-23 22:33 ` Benjamin Herrenschmidt
2020-07-24 8:14 ` Arnd Bergmann
2020-07-24 8:14 ` Arnd Bergmann
2020-07-24 8:14 ` Arnd Bergmann
2020-07-24 8:14 ` Arnd Bergmann
2020-06-07 7:59 ` [PATCH v5 2/4] riscv: Introduce CONFIG_RELOCATABLE Alexandre Ghiti
2020-06-07 7:59 ` Alexandre Ghiti
2020-06-10 14:10 ` Jerome Forissier
2020-06-11 19:43 ` Alex Ghiti
2020-06-07 7:59 ` [PATCH v5 3/4] powerpc: Move script to check relocations at compile time in scripts/ Alexandre Ghiti
2020-06-07 7:59 ` Alexandre Ghiti
2020-06-07 7:59 ` [PATCH v5 4/4] riscv: Check relocations at compile time Alexandre Ghiti
2020-06-07 7:59 ` Alexandre Ghiti
2020-07-08 4:21 ` [PATCH v5 0/4] vmalloc kernel mapping and relocatable kernel Alex Ghiti
2020-07-08 4:21 ` Alex Ghiti
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