From: Al Viro
> Sent: 13 June 2020 16:31
> On Sat, Jun 13, 2020 at 07:12:36PM +0530, afzal mohammed wrote:
> > Hi,
> >
> > On Sat, Jun 13, 2020 at 01:56:15PM +0100, Al Viro wrote:
> >
> > > Incidentally, what about get_user()/put_user()? _That_ is where it's
> > > going to really hurt...
> >
> > A
Hi,
On Sun, Jun 14, 2020 at 06:51:43PM +0530, afzal mohammed wrote:
> It is MB/s for copying one file to another via user space buffer, i.e.
> the value coreutils 'dd' shows w/ status=progress (here it was busybox
> 'dd', so instead it was enabling a compile time option)
Just for correctness, st
Hi,
On Sat, Jun 13, 2020 at 10:45:33PM +0200, Arnd Bergmann wrote:
> 4% boot time increase sounds like a lot, especially if that is only for
> copy_from_user/copy_to_user. In the end it really depends on how well
> get_user()/put_user() and small copies can be optimized in the end.
i mentioned t
Hi,
On Sat, Jun 13, 2020 at 02:15:52PM +0100, Russell King - ARM Linux admin wrote:
> On Sat, Jun 13, 2020 at 05:34:32PM +0530, afzal mohammed wrote:
> > i think C
> > library cuts any size read, write to page size (if it exceeds) &
> > invokes the system call.
> You can't make that assumption a
On Sat, Jun 13, 2020 at 10:45:33PM +0200, Arnd Bergmann wrote:
> On Sat, Jun 13, 2020 at 2:04 PM afzal mohammed
> wrote:
> > Observation is that max. pages reaching copy_{from,to}_user() is 2,
> > observed maximum of n (number of bytes) being 1 page size. i think C
> > library cuts any size read,
On Sat, Jun 13, 2020 at 2:04 PM afzal mohammed wrote:
> On Fri, Jun 12, 2020 at 10:07:28PM +0200, Arnd Bergmann wrote:
>
> > I think a lot
> > of usercopy calls are only for a few bytes, though this is of course
> > highly workload dependent and you might only care about the large
> > ones.
>
> Ob
On Sat, Jun 13, 2020 at 6:00 PM Al Viro wrote:
> On Sat, Jun 13, 2020 at 04:41:18PM +0100, Al Viro wrote:
> > On Sat, Jun 13, 2020 at 04:31:02PM +0100, Al Viro wrote:
> > > On Sat, Jun 13, 2020 at 07:12:36PM +0530, afzal mohammed wrote:
> > > > Hi,
> > > >
> > > > On Sat, Jun 13, 2020 at 01:56:15P
On Sat, Jun 13, 2020 at 04:41:18PM +0100, Al Viro wrote:
> On Sat, Jun 13, 2020 at 04:31:02PM +0100, Al Viro wrote:
> > On Sat, Jun 13, 2020 at 07:12:36PM +0530, afzal mohammed wrote:
> > > Hi,
> > >
> > > On Sat, Jun 13, 2020 at 01:56:15PM +0100, Al Viro wrote:
> > >
> > > > Incidentally, what a
On Sat, Jun 13, 2020 at 04:31:02PM +0100, Al Viro wrote:
> On Sat, Jun 13, 2020 at 07:12:36PM +0530, afzal mohammed wrote:
> > Hi,
> >
> > On Sat, Jun 13, 2020 at 01:56:15PM +0100, Al Viro wrote:
> >
> > > Incidentally, what about get_user()/put_user()? _That_ is where it's
> > > going to really
On Sat, Jun 13, 2020 at 07:12:36PM +0530, afzal mohammed wrote:
> Hi,
>
> On Sat, Jun 13, 2020 at 01:56:15PM +0100, Al Viro wrote:
>
> > Incidentally, what about get_user()/put_user()? _That_ is where it's
> > going to really hurt...
>
> All other uaccess routines are also planned to be added,
Hi,
On Sat, Jun 13, 2020 at 01:56:15PM +0100, Al Viro wrote:
> Incidentally, what about get_user()/put_user()? _That_ is where it's
> going to really hurt...
All other uaccess routines are also planned to be added, posting only
copy_{from,to}_user() was to get early feedback (mentioned in the
c
Hi,
On Sat, Jun 13, 2020 at 02:08:11PM +0300, Andy Shevchenko wrote:
> On Fri, Jun 12, 2020 at 1:20 PM afzal mohammed
> wrote:
> > +// Started from arch/um/kernel/skas/uaccess.c
>
> Does it mean you will deduplicate it there?
What i meant was, that file was taken as a template & nothing more,
On Sat, Jun 13, 2020 at 05:34:32PM +0530, afzal mohammed wrote:
> Hi,
>
> On Fri, Jun 12, 2020 at 10:07:28PM +0200, Arnd Bergmann wrote:
>
> > I think a lot
> > of usercopy calls are only for a few bytes, though this is of course
> > highly workload dependent and you might only care about the lar
On Sat, Jun 13, 2020 at 01:51:26PM +0100, Al Viro wrote:
> On Sat, Jun 13, 2020 at 05:34:32PM +0530, afzal mohammed wrote:
>
> > Observation is that max. pages reaching copy_{from,to}_user() is 2,
> > observed maximum of n (number of bytes) being 1 page size. i think C
> > library cuts any size re
On Sat, Jun 13, 2020 at 05:34:32PM +0530, afzal mohammed wrote:
> Observation is that max. pages reaching copy_{from,to}_user() is 2,
> observed maximum of n (number of bytes) being 1 page size. i think C
> library cuts any size read, write to page size (if it exceeds) &
> invokes the system call.
Hi,
On Fri, Jun 12, 2020 at 10:07:28PM +0200, Arnd Bergmann wrote:
> I think a lot
> of usercopy calls are only for a few bytes, though this is of course
> highly workload dependent and you might only care about the large
> ones.
Observation is that max. pages reaching copy_{from,to}_user() is 2
On Fri, Jun 12, 2020 at 1:20 PM afzal mohammed wrote:
>
> copy_{from,to}_user() uaccess helpers are implemented by user page
> pinning, followed by temporary kernel mapping & then memcpy(). This
> helps to achieve user page copy when current virtual address mapping
> of the CPU excludes user pages
On Fri, Jun 12, 2020 at 3:55 PM afzal mohammed wrote:
> On Fri, Jun 12, 2020 at 02:02:13PM +0200, Arnd Bergmann wrote:
> > On Fri, Jun 12, 2020 at 12:18 PM afzal mohammed
> > wrote:
>
> > > Roughly a one-third drop in performance. Disabling highmem improves
> > > performance only slightly.
>
> >
Hi,
On Fri, Jun 12, 2020 at 02:02:13PM +0200, Arnd Bergmann wrote:
> On Fri, Jun 12, 2020 at 12:18 PM afzal mohammed
> wrote:
> > Roughly a one-third drop in performance. Disabling highmem improves
> > performance only slightly.
> There are probably some things that can be done to optimize it,
On Fri, Jun 12, 2020 at 12:18 PM afzal mohammed wrote:
>
> copy_{from,to}_user() uaccess helpers are implemented by user page
> pinning, followed by temporary kernel mapping & then memcpy(). This
> helps to achieve user page copy when current virtual address mapping
> of the CPU excludes user page
copy_{from,to}_user() uaccess helpers are implemented by user page
pinning, followed by temporary kernel mapping & then memcpy(). This
helps to achieve user page copy when current virtual address mapping
of the CPU excludes user pages.
Performance wise, results are not encouraging, 'dd' on tmpfs r
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