[PATCH v5 00/25] Add perf support to the rockchip-dfi driver

[Vincent Legoll]

Hi,

On Wed, Jun 14, 2023 at 3:27 PM Sebastian Reichel
<sebastian.reichel at 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 have been running this in a loop with varying sleep duration for
the last few hours without hitting it, with and without memtester.

REPEATS=1000
MAX_DURATION=100

OUT="/tmp/perf-dfi-rk3588-${REPEATS}x${MAX_DURATION}s.txt"
echo -n > $OUT

for i in $(seq $REPEATS) ; do
  DURATION=$(shuf -i "0-${MAX_DURATION}" -n 1)
  echo -n "${DURATION} : " >> $OUT
  perf stat -a -e rockchip_ddr/cycles/ sleep $DURATION 2>&1 | awk
'/rockchip_ddr/ {printf("%X\n", int($1))}' >> $OUT
done

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

-- 
Vincent Legoll