On Mon, Aug 09, 2021 at 07:44:50PM +0900, Chanho Park wrote:
> From: Will Deacon <will@xxxxxxxxxx>
>
> commit 77ec462536a13d4b428a1eead725c4818a49f0b1 upstream.
> (The upstream patch was not marked as fixed but this can fix
> Fixes: 28b1a824a4f4 ("arm64: vdso: Substitute gettimeofday() with C implementation")
> sysbench memory comparison:
> - Before: 3072.00 MB transferred (2601.11 MB/sec)
> - After: 3072.00 MB transferred (3217.86 MB/sec)
> )
>
> We can avoid the expensive ISB instruction after reading the counter in
> the vDSO gettime functions by creating a fake address hazard against a
> dummy stack read, just like we do inside the kernel.
>
> Fixes: 28b1a824a4f4 ("arm64: vdso: Substitute gettimeofday() with C implementation")
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> Link: https://lore.kernel.org/r/20210318170738.7756-5-will@xxxxxxxxxx
> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Chanho Park <chanho61.park@xxxxxxxxxxx>
> ---
> I found this regression while executing below sysbench benchmark command.
> It showed lower score compared with internal 4.19 version. The
> regression can be seen from 5.4/5.10 kernel version.
Now queued up, thanks.
greg k-h
