Le 17/01/2020 à 09:58, Segher Boessenkool a écrit :

Hi!

On Thu, Jan 16, 2020 at 05:58:24PM +0000, Christophe Leroy wrote:

quoted

On a powerpc8xx, with current powerpc/32 ASM VDSO:

gettimeofday:    vdso: 907 nsec/call
clock-getres-realtime:    vdso: 484 nsec/call
clock-gettime-realtime:    vdso: 899 nsec/call

The first patch adds VDSO generic C support without any changes to common code.
Performance is as follows:

gettimeofday:    vdso: 1211 nsec/call
clock-getres-realtime:    vdso: 722 nsec/call
clock-gettime-realtime:    vdso: 1216 nsec/call

Then a few changes in the common code have allowed performance improvement. At
the end of the series we have:

gettimeofday:    vdso: 974 nsec/call
clock-getres-realtime:    vdso: 545 nsec/call
clock-gettime-realtime:    vdso: 941 nsec/call

The final result is rather close to pure ASM VDSO:
* 7% more on gettimeofday (9 cycles)
* 5% more on clock-gettime-realtime (6 cycles)
* 12% more on clock-getres-realtime (8 cycles)

Nice!  Much better.

It should be tested on more representative hardware, too, but this looks
promising alright :-)

Yes.

Now the challenge is to get VDSO32 buildable on PPC64. The big issue is 
that in most powerpc/include/asm/*.h , CONFIG_PPC64 is used to know if 
the build is a 64 bits build or a 32 bits build, so VDSO32 build fails.

I don't know how this could be easily fixed.

Christophe

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel