Re: [RFC 0/3] ARM: copy_{from,to}_user() for vmsplit 4g/4g

Nicolas Pitre
2020-06-12T15:19:33Z

On Fri, 12 Jun 2020, afzal mohammed wrote:

> Performance wise, results are not encouraging, 'dd' on tmpfs results,
>
> ARM Cortex-A8, BeagleBone White (256MiB RAM):
> w/o series - ~29.5 MB/s
> w/ series - ~20.5 MB/s
> w/ series & highmem disabled - ~21.2 MB/s
>
> On Cortex-A15(2GiB RAM) in QEMU:
> w/o series - ~4 MB/s
> w/ series - ~2.6 MB/s
>
> Roughly a one-third drop in performance. Disabling highmem improves
> performance only slightly.

Could you compare with CONFIG_UACCESS_WITH_MEMCPY as well?

Nicolas