Hi,

On Wed, Jun 14, 2023 at 07:51:21PM +0000, Vincent Legoll wrote:
> On Wed, Jun 14, 2023 at 3:27 PM Sebastian Reichel
> <sebastian.reichel@collabora.com> wrote:
> > On Wed, Jun 14, 2023 at 03:40:34PM +0200, Sebastian Reichel wrote:
> > > I tested the series on RK3588 EVB1. The read/write byts looks
> > > sensible. Sometimes cycles reads unrealistic values, though:
> > >
> > > 18446744070475110400      rockchip_ddr/cycles/
> >
> > I have seen this going off a few times with and without memory
> > pressure. If it's way off, it always seems to follow the same
> > pattern: The upper 32 bits are 0xffffffff instead of 0x00000000
> > with the lower 32 bits containing sensible data.
> 
> How often is that happening ?

I saw it multiple times (4 or 5) within a few tries (I guess around
20). I could see it with and without applying load on the memory.
Tests have been running globally for a second using 'sleep 1' (just
like the example from Sascha Hauer in the perf patch)

> BTW, it's on a musl-libc arm64 void linux userspace.

In my case it's Debian unstable.

-- Sebastian