Re: [PATCH v3 21/26] arm64: Introduce asm/vdso/arch_timer.h

Catalin Marinas
2020-03-15T18:32:16Z

On Fri, Mar 13, 2020 at 03:43:40PM +0000, Vincenzo Frascino wrote:
> The vDSO library should only include the necessary headers required for
> a userspace library (UAPI and a minimal set of kernel headers). To make
> this possible it is necessary to isolate from the kernel headers the
> common parts that are strictly necessary to build the library.
>
> Introduce asm/vdso/arch_timer.h to contain all the arm64 specific
> code. This allows to replace the second isb() in __arch_get_hw_counter()
> with a fake dependent stack read of the counter which improves the vdso
> library peformances of ~4.5%. Below the results of vdsotest [1] ran for
> 100 iterations.

The subject seems to imply a non-functional change but as you read, it
gets a lot more complicated. Could you keep the functional change
separate from the header clean-up, maybe submit it as an independent
patch? And it shouldn't go in without Will's ack ;).

--
Catalin