Christophe Leroy <christophe.le...@c-s.fr> writes: > Le 13/09/2019 à 15:31, Santosh Sivaraj a écrit : >> Christophe Leroy <christophe.le...@c-s.fr> writes: >> >>> Hi Santosh, >>> >>> Le 26/08/2019 à 07:44, Santosh Sivaraj a écrit : >>>> Hi Christophe, >>>> >>>> Christophe Leroy <christophe.le...@c-s.fr> writes: >>>> >>>>> __get_datapage() is only a few instructions to retrieve the >>>>> address of the page where the kernel stores data to the VDSO. >>>>> >>>>> By inlining this function into its users, a bl/blr pair and >>>>> a mflr/mtlr pair is avoided, plus a few reg moves. >>>>> >>>>> The improvement is noticeable (about 55 nsec/call on an 8xx) >>>>> >>>>> vdsotest before the patch: >>>>> gettimeofday: vdso: 731 nsec/call >>>>> clock-gettime-realtime-coarse: vdso: 668 nsec/call >>>>> clock-gettime-monotonic-coarse: vdso: 745 nsec/call >>>>> >>>>> vdsotest after the patch: >>>>> gettimeofday: vdso: 677 nsec/call >>>>> clock-gettime-realtime-coarse: vdso: 613 nsec/call >>>>> clock-gettime-monotonic-coarse: vdso: 690 nsec/call >>>>> >>>>> Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> >>>>> --- >>>>> arch/powerpc/kernel/vdso32/cacheflush.S | 10 +++++----- >>>>> arch/powerpc/kernel/vdso32/datapage.S | 29 >>>>> ++++------------------------- >>>>> arch/powerpc/kernel/vdso32/datapage.h | 11 +++++++++++ >>>>> arch/powerpc/kernel/vdso32/gettimeofday.S | 13 ++++++------- >>>>> 4 files changed, 26 insertions(+), 37 deletions(-) >>>>> create mode 100644 arch/powerpc/kernel/vdso32/datapage.h >>>> >>>> The datapage.h file should ideally be moved under include/asm, then we can >>>> use >>>> the same for powerpc64 too. >>> >>> I have a more ambitious project indeed. >>> >>> Most of the VDSO code is duplicated between vdso32 and vdso64. I'm >>> aiming at merging everything into a single source code. >>> >>> This means we would have to generate vdso32.so and vdso64.so out of the >>> same source files. Any idea on how to do that ? I'm not too good at >>> creating Makefiles. I guess we would have everything in >>> arch/powerpc/kernel/vdso/ and would have to build the objects twice, >>> once in arch/powerpc/kernel/vdso32/ and once in arch/powerpc/kernel/vdso64/ >> >> Should we need to build the objects twice? For 64 bit config it is going to >> be >> a 64 bit build else a 32 bit build. It should suffice to get the single >> source >> code compile for both, maybe with macros or (!)CONFIG_PPC64 conditional >> compilation. Am I missing something when you say build twice? >> > > IIUC, on PPC64 we build vdso64 for 64bits user apps and vdso32 for > 32bits user apps. > > In arch/powerpc/kernel/Makefile, you have: > > obj-$(CONFIG_VDSO32) += vdso32/ > obj-$(CONFIG_PPC64) += vdso64/ > > And in arch/powerpc/platforms/Kconfig.cputype, you have: > > config VDSO32 > def_bool y > depends on PPC32 || CPU_BIG_ENDIAN > help > This symbol controls whether we build the 32-bit VDSO. We obviously > want to do that if we're building a 32-bit kernel. If we're building > a 64-bit kernel then we only want a 32-bit VDSO if we're building for > big endian. That is because the only little endian configuration we > support is ppc64le which is 64-bit only. >
I didn't know we build 32 bit vdso for 64 bit big endians. But I don't think its difficult to do it, might be a bit tricky. We can have two targets from the same source. SRC = vdso/*.c OBJS_32 = $(SRC:.c=vdso32/.o) OBJS_64 = $(SRC:.c=vdso64/.o) Something like this would work. Of course, this is out of memory, might have to do something slightly different for the Makefiles in kernel. Thanks, Santosh > > > > Christophe
