| Message ID | 20210107221724.10036-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/5] drm/i915/selftests: Skip unstable timing measurements | expand |
Hi Chris, > diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > index 75839db63bea..59c58a276677 100644 > --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c > +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, > } > > sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); > + if (!t[0]) > + continue; > + are you assuming here that if t[0] is '0', also the rest of 't' is '0'? Andi > pr_info("%s src(%s, %s) -> dst(%s, %s) %14s %4llu KiB copy: %5lld MiB/s\n", > __func__, > src_mr->name,
Quoting Andi Shyti (2021-01-08 12:26:45) > Hi Chris, > > > diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > index 75839db63bea..59c58a276677 100644 > > --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, > > } > > > > sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); > > + if (!t[0]) > > + continue; > > + > > are you assuming here that if t[0] is '0', also the rest of 't' > is '0'? It's sorted into ascending order with ktime_t... Hmm, s64 not u64 as I presumed. So better to check <= 0. -Chris
Hi Chris, > > > diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > index 75839db63bea..59c58a276677 100644 > > > --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, > > > } > > > > > > sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); > > > + if (!t[0]) > > > + continue; > > > + > > > > are you assuming here that if t[0] is '0', also the rest of 't' > > is '0'? > > It's sorted into ascending order with ktime_t... Hmm, s64 not u64 as I > presumed. So better to check <= 0. by division by 0 I guess you mean here: div64_u64(mul_u32_u32(4 * size, 1000 * 1000 * 1000), t[1] + 2 * t[2] + t[3]) >> 20); why are you testing t[0]? Did I miss anything else? Andi
Quoting Andi Shyti (2021-01-08 13:51:54) > Hi Chris, > > > > > diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > index 75839db63bea..59c58a276677 100644 > > > > --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, > > > > } > > > > > > > > sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); > > > > + if (!t[0]) > > > > + continue; > > > > + > > > > > > are you assuming here that if t[0] is '0', also the rest of 't' > > > is '0'? > > > > It's sorted into ascending order with ktime_t... Hmm, s64 not u64 as I > > presumed. So better to check <= 0. > > by division by 0 I guess you mean here: > > div64_u64(mul_u32_u32(4 * size, > 1000 * 1000 * 1000), > t[1] + 2 * t[2] + t[3]) >> 20); > > why are you testing t[0]? Did I miss anything else? Since t[0] is the most negative value, if it is <= 0 that implies at least one of the measurements was bad. If any are bad, all are bad by association. I considered checking t[4] to make sure that at least the best was good enough, but paranoia won. -Chris
Hi Chris, > > > > > diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > > index 75839db63bea..59c58a276677 100644 > > > > > --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > > +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c > > > > > @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, > > > > > } > > > > > > > > > > sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); > > > > > + if (!t[0]) > > > > > + continue; > > > > > + > > > > > > > > are you assuming here that if t[0] is '0', also the rest of 't' > > > > is '0'? > > > > > > It's sorted into ascending order with ktime_t... Hmm, s64 not u64 as I > > > presumed. So better to check <= 0. > > > > by division by 0 I guess you mean here: > > > > div64_u64(mul_u32_u32(4 * size, > > 1000 * 1000 * 1000), > > t[1] + 2 * t[2] + t[3]) >> 20); > > > > why are you testing t[0]? Did I miss anything else? > > Since t[0] is the most negative value, if it is <= 0 that implies at > least one of the measurements was bad. If any are bad, all are bad by > association. I considered checking t[4] to make sure that at least the > best was good enough, but paranoia won. yes, that's what I actually meant with the first question. Thanks, Andi
diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c index 75839db63bea..59c58a276677 100644 --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c @@ -852,6 +852,9 @@ static int _perf_memcpy(struct intel_memory_region *src_mr, } sort(t, ARRAY_SIZE(t), sizeof(*t), wrap_ktime_compare, NULL); + if (!t[0]) + continue; + pr_info("%s src(%s, %s) -> dst(%s, %s) %14s %4llu KiB copy: %5lld MiB/s\n", __func__, src_mr->name,
If any of the perf tests run into 0 time, not only are we liable to divide by zero, but the result would be highly questionable. Nevertheless, let's not have a div-by-zero error. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> --- drivers/gpu/drm/i915/selftests/intel_memory_region.c | 3 +++ 1 file changed, 3 insertions(+)