Christophe,
Christophe Leroy writes:
> On 01/09/2020 02:05 PM, Thomas Gleixner wrote:
>> The reason why this is implemented in this way is that
>> __arch_get_hw_counter() needs a way to express that the clocksource of
>> the moment is not suitable for VDSO so that the syscall fallback gets
>>
Hi Thomas,
On 01/09/2020 02:05 PM, Thomas Gleixner wrote:
Christophe!
Christophe Leroy writes:
In do_hres(), I see:
cycles = __arch_get_hw_counter(vd->clock_mode);
ns = vdso_ts->nsec;
last = vd->cycle_last;
if
Christophe!
Christophe Leroy writes:
> In do_hres(), I see:
>
> cycles = __arch_get_hw_counter(vd->clock_mode);
> ns = vdso_ts->nsec;
> last = vd->cycle_last;
> if (unlikely((s64)cycles < 0))
> return -1;
>
>
Hi Thomas,
In do_hres(), I see:
cycles = __arch_get_hw_counter(vd->clock_mode);
ns = vdso_ts->nsec;
last = vd->cycle_last;
if (unlikely((s64)cycles < 0))
return -1;
__arch_get_hw_counter() returns a u64
On Sun, Oct 27, 2019 at 10:21:25AM +0100, Christophe Leroy wrote:
> Le 27/10/2019 à 01:06, Segher Boessenkool a écrit :
> >The hand-optimised asm code will pretty likely win handsomely, whatever
> >you do. Especially on cores like the 885 (no branch prediction, single
> >issue, small caches,
Le 27/10/2019 à 01:06, Segher Boessenkool a écrit :
On Sat, Oct 26, 2019 at 08:48:27PM +0200, Thomas Gleixner wrote:
On Sat, 26 Oct 2019, Christophe Leroy wrote:
Let's look at the code:
__cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
const struct
On Sat, Oct 26, 2019 at 08:48:27PM +0200, Thomas Gleixner wrote:
> On Sat, 26 Oct 2019, Christophe Leroy wrote:
> Let's look at the code:
>
> __cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
> {
> const struct vdso_data *vd = __arch_get_vdso_data();
>
>
On Sat, 26 Oct 2019, Christophe Leroy wrote:
> Le 26/10/2019 à 17:53, Thomas Gleixner a écrit :
> > > > > > gettimeofday: vdso: 750 nsec/call
> > > > > >
> > > > > > gettimeofday: vdso: 1533 nsec/call
> > > >
> > > > Small improvement (3%) with the proposed change:
> > > >
> > > >
Le 26/10/2019 à 17:53, Thomas Gleixner a écrit :
On Tue, 22 Oct 2019, Christophe Leroy wrote:
Le 22/10/2019 à 11:01, Christophe Leroy a écrit :
Le 21/10/2019 à 23:29, Thomas Gleixner a écrit :
On Mon, 21 Oct 2019, Christophe Leroy wrote:
This is a tentative to switch powerpc/32 vdso to
Le 26/10/2019 à 15:55, Andy Lutomirski a écrit :
On Tue, Oct 22, 2019 at 6:56 AM Christophe Leroy
wrote:
The performance is rather disappoiting. That's most likely all
calculation in the C implementation are based on 64 bits math and
converted to 32 bits at the very end. I guess C
On Tue, 22 Oct 2019, Christophe Leroy wrote:
> Le 22/10/2019 à 11:01, Christophe Leroy a écrit :
> > Le 21/10/2019 à 23:29, Thomas Gleixner a écrit :
> > > On Mon, 21 Oct 2019, Christophe Leroy wrote:
> > >
> > > > This is a tentative to switch powerpc/32 vdso to generic C
> > > > implementation.
On Tue, Oct 22, 2019 at 6:56 AM Christophe Leroy
wrote:
>
>
> >>> The performance is rather disappoiting. That's most likely all
> >>> calculation in the C implementation are based on 64 bits math and
> >>> converted to 32 bits at the very end. I guess C implementation should
> >>> use 32 bits
Le 22/10/2019 à 11:01, Christophe Leroy a écrit :
Le 21/10/2019 à 23:29, Thomas Gleixner a écrit :
On Mon, 21 Oct 2019, Christophe Leroy wrote:
This is a tentative to switch powerpc/32 vdso to generic C
implementation.
It will likely not work on 64 bits or even build properly at the
Le 21/10/2019 à 23:29, Thomas Gleixner a écrit :
On Mon, 21 Oct 2019, Christophe Leroy wrote:
This is a tentative to switch powerpc/32 vdso to generic C implementation.
It will likely not work on 64 bits or even build properly at the moment.
powerpc is a bit special for VDSO as well as
On Mon, 21 Oct 2019, Christophe Leroy wrote:
> This is a tentative to switch powerpc/32 vdso to generic C implementation.
> It will likely not work on 64 bits or even build properly at the moment.
>
> powerpc is a bit special for VDSO as well as system calls in the
> way that it requires setting
This is a tentative to switch powerpc/32 vdso to generic C implementation.
It will likely not work on 64 bits or even build properly at the moment.
powerpc is a bit special for VDSO as well as system calls in the
way that it requires setting CR SO bit which cannot be done in C.
Therefore,
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