On Wed, Feb 7, 2018 at 9:05 AM, Linus Torvalds
wrote:
>
> The other thing we need to do is to just pass down the system call
> number as an argument instead of reloading it.
.. we may also want to disable some debug things.
For example, if you enable KASAN, it does insane things for
do_syscall()
On Wed, Feb 7, 2018 at 7:18 AM, Andi Kleen wrote:
>
> Fast path saves more than just register saving. I changed the fast path
> to save all registers in my earlier clearregs branches
I know. I saw your patches. And I went "Eww".
> It is still quite a bit faster than all the slow stuff the C do_
> Plus the fastpath couldn't clear those registers anyway, since it
> didn't even _save_ them - exactly because the whole point of the
> fastpath was that not all registers are clobbered by the calling
> conventions.
Fast path saves more than just register saving. I changed the fast path
to save
On Tue, Feb 6, 2018 at 3:54 PM, Andi Kleen wrote:
>
> But for push, on older CPUs (older AMD, most Atoms, really old Intel big core)
> sub+mov is a lot faster than push because push has additional dependencies
> causing pipeline bubbles. So you would make these cases slower if you
> use PUSH.
I r
> The reason for that complexity is purely the system call fastpath case
> that no longer exists, I think.
>
> Am I missing something?
Yes merging the macros should be fine without fast path.
But for push, on older CPUs (older AMD, most Atoms, really old Intel big core)
sub+mov is a lot faster
On Tue, Feb 6, 2018 at 10:48 PM, Linus Torvalds
wrote:
> On Tue, Feb 6, 2018 at 1:32 PM, Dominik Brodowski
> wrote:
>> Same as is done for syscalls, interleave XOR with PUSH or MOV
>> instructions for exceptions/interrupts, in order to minimize
>> the cost of the additional instructions required
On Tue, Feb 6, 2018 at 1:32 PM, Dominik Brodowski
wrote:
> Same as is done for syscalls, interleave XOR with PUSH or MOV
> instructions for exceptions/interrupts, in order to minimize
> the cost of the additional instructions required for register
> clearing.
Side note: I would _really_ like to s
On Tue, Feb 6, 2018 at 1:32 PM, Dominik Brodowski
wrote:
> Same as is done for syscalls, interleave XOR with PUSH or MOV
> instructions for exceptions/interrupts, in order to minimize
> the cost of the additional instructions required for register
> clearing.
>
> Signed-off-by: Dominik Brodowski
Same as is done for syscalls, interleave XOR with PUSH or MOV
instructions for exceptions/interrupts, in order to minimize
the cost of the additional instructions required for register
clearing.
Signed-off-by: Dominik Brodowski
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
ind
9 matches
Mail list logo
