linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Linus Walleij <linus.walleij@linaro.org>
To: afzal mohammed <afzal.mohd.ma@gmail.com>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: ARM: vmsplit 4g/4g
Date: Wed, 10 Jun 2020 12:10:21 +0200	[thread overview]
Message-ID: <CACRpkdboPBGBdHaRtZ=OAFvikYZVh=BVu192uyiB8T=yeHHEbA@mail.gmail.com> (raw)
In-Reply-To: <20200608110902.GA5736@afzalpc>

On Mon, Jun 8, 2020 at 1:09 PM afzal mohammed <afzal.mohd.ma@gmail.com> wrote:
> On Sun, Jun 07, 2020 at 05:11:16PM +0100, Russell King - ARM Linux admin wrote:
> > On Sun, Jun 07, 2020 at 06:29:32PM +0530, afzal mohammed wrote:
>
> > > get_user_pages_fast() followed by kmap_atomic() & then memcpy() seems
> > > to work in principle for user copy.
> >
> > Have you done any performance evaluation of the changes yet? I think
> > it would be a good idea to keep that in the picture. If there's any
> > significant regression, then that will need addressing.
>
> Not yet. Yes, i will do the performance evaluation.
>
> i am also worried about the impact on performance as these
> [ get_user_pages() or friends, kmap_atomic() ] are additionally
> invoked in the copy_{from,to}_user() path now.

I am happy to help!

I am anyway working on MMU-related code (KASan) so I need to be on
top of this stuff.

What test is appropriate for this? I would intuitively think hackbench?

> Note that this was done on a topic branch for user copy. Changes for
> kernel static mapping to vmalloc has not been merged with these.
> Also having kernel lowmem w/ a separate asid & switching at kernel
> entry/exit b/n user & kernel lowmem by changing ttbr0 is yet to be
> done. Quite a few things remaining to be done to achieve vmsplit 4g/4g

I will be very excited to look at patches or a git branch once you have
something you want to show. Also to just understand how you go about
this. I have several elder systems under my
roof so my contribution could hopefully be to help and debug any issues
on these.

Yours,
Linus Walleij

  reply	other threads:[~2020-06-10 10:10 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-31  9:32 [PATCH 0/3] Highmem support for 32-bit RISC-V Eric Lin
2020-03-31  9:32 ` [PATCH 1/3] riscv/mm: Add pkmap region and CONFIG_HIGHMEM Eric Lin
2020-03-31  9:32 ` [PATCH 2/3] riscv/mm: Implement kmap() and kmap_atomic() Eric Lin
2020-03-31  9:32 ` [PATCH 3/3] riscv/mm: Add pkmap in print_vm_layout() Eric Lin
2020-04-02  9:31 ` [PATCH 0/3] Highmem support for 32-bit RISC-V Arnd Bergmann
2020-04-08  3:51   ` Alan Kao
2020-04-08 14:40     ` Arnd Bergmann
2020-04-14 15:17       ` afzal mohammed
2020-04-14 19:29         ` Arnd Bergmann
2020-04-15 13:54           ` afzal mohammed
2020-05-03 14:50             ` afzal mohammed
2020-05-03 20:20               ` Arnd Bergmann
2020-05-04  9:10                 ` afzal mohammed
2020-05-04 11:27                   ` Arnd Bergmann
2020-05-11 14:21                     ` ARM: static kernel in vmalloc space (was Re: [PATCH 0/3] Highmem support for 32-bit RISC-V) afzal mohammed
2020-05-11 15:29                       ` Arnd Bergmann
2020-05-12 10:47                         ` ARM: static kernel in vmalloc space afzal mohammed
2020-05-12 19:49                           ` Arnd Bergmann
2020-05-14 11:17                             ` afzal mohammed
2020-05-14 12:41                               ` Arnd Bergmann
2020-05-14 13:35                                 ` afzal mohammed
2020-05-14 14:44                                   ` afzal mohammed
2020-05-14 15:32                                   ` Arnd Bergmann
2020-05-16  6:06                                     ` afzal mohammed
2020-05-16  7:35                                       ` Arnd Bergmann
2020-06-07 12:59                                         ` ARM: vmsplit 4g/4g afzal mohammed
2020-06-07 16:11                                           ` Russell King - ARM Linux admin
2020-06-08 11:09                                             ` afzal mohammed
2020-06-10 10:10                                               ` Linus Walleij [this message]
2020-06-12 10:25                                                 ` afzal mohammed
2020-06-15  9:11                                                   ` Linus Walleij
2020-06-15 10:01                                                     ` afzal mohammed
2020-06-07 19:26                                           ` Arnd Bergmann
2020-06-08 11:18                                             ` afzal mohammed
2020-06-08 14:43                                               ` Arnd Bergmann
2020-06-08 15:17                                                 ` afzal mohammed
2020-06-09 12:15                                                   ` afzal mohammed
2020-06-09 14:22                                                     ` Arnd Bergmann
2020-05-14 16:25                                 ` ARM: static kernel in vmalloc space Russell King - ARM Linux admin
2020-05-14 21:12                                   ` Arnd Bergmann
2020-05-14 23:40                                     ` Russell King - ARM Linux admin
2020-05-15 15:41                                       ` Arnd Bergmann
2020-07-30  9:33                                         ` Linus Walleij
2020-07-30 10:17                                           ` Arnd Bergmann

Reply instructions:

You may reply publicly 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='CACRpkdboPBGBdHaRtZ=OAFvikYZVh=BVu192uyiB8T=yeHHEbA@mail.gmail.com' \
    --to=linus.walleij@linaro.org \
    --cc=afzal.mohd.ma@gmail.com \
    --cc=arnd@arndb.de \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).