On 7 November 2016 at 19:49, Robert Bragg <rob...@sixbynine.org> wrote: > The maximum OA sampling frequency is now configurable via a > dev.i915.oa_max_sample_rate sysctl parameter. > > Following the precedent set by perf's similar > kernel.perf_event_max_sample_rate the default maximum rate is 100000Hz > > Signed-off-by: Robert Bragg <rob...@sixbynine.org> > --- > drivers/gpu/drm/i915/i915_perf.c | 61 > ++++++++++++++++++++++++++++++++-------- > 1 file changed, 50 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_perf.c > b/drivers/gpu/drm/i915/i915_perf.c > index e51c1d8..1a87fe9 100644 > --- a/drivers/gpu/drm/i915/i915_perf.c > +++ b/drivers/gpu/drm/i915/i915_perf.c > @@ -82,6 +82,21 @@ static u32 i915_perf_stream_paranoid = true; > #define INVALID_CTX_ID 0xffffffff > > > +/* For sysctl proc_dointvec_minmax of i915_oa_max_sample_rate > + * > + * 160ns is the smallest sampling period we can theoretically program the OA > + * unit with on Haswell, corresponding to 6.25MHz. > + */ > +static int oa_sample_rate_hard_limit = 6250000; > + > +/* Theoretically we can program the OA unit to sample every 160ns but don't > + * allow that by default unless root... > + * > + * The default threshold of 100000Hz is based on perf's similar > + * kernel.perf_event_max_sample_rate sysctl parameter. > + */ > +static u32 i915_oa_max_sample_rate = 100000; > + > /* XXX: beware if future OA HW adds new report formats that the current > * code assumes all reports have a power-of-two size and ~(size - 1) can > * be used as a mask to align the OA tail pointer. > @@ -1314,6 +1329,7 @@ static int read_properties_unlocked(struct > drm_i915_private *dev_priv, > } > > for (i = 0; i < n_props; i++) { > + u64 oa_period, oa_freq_hz; > u64 id, value; > int ret; > > @@ -1359,21 +1375,35 @@ static int read_properties_unlocked(struct > drm_i915_private *dev_priv, > return -EINVAL; > } > > - /* NB: The exponent represents a period as follows: > - * > - * 80ns * 2^(period_exponent + 1) > - * > - * Theoretically we can program the OA unit to sample > + /* Theoretically we can program the OA unit to sample > * every 160ns but don't allow that by default unless > * root. > * > - * Referring to perf's > - * kernel.perf_event_max_sample_rate for a precedent > - * (100000 by default); with an OA exponent of 6 we > get > - * a period of 10.240 microseconds -just under > 100000Hz > + * On Haswell the period is derived from the exponent > + * as: > + * > + * period = 80ns * 2^(exponent + 1) > + */ > + BUILD_BUG_ON(sizeof(oa_period) != 8); > + oa_period = 80ull * (2ull << value); > + > + /* This check is primarily to ensure that oa_period <= > + * UINT32_MAX (before passing to do_div which only > + * accepts a u32 denominator), but we can also skip > + * checking anything < 1Hz which implicitly can't be > + * limited via an integer oa_max_sample_rate. > */ > - if (value < 6 && !capable(CAP_SYS_ADMIN)) { > - DRM_ERROR("Minimum OA sampling exponent is 6 > without root privileges\n"); > + if (oa_period <= NSEC_PER_SEC) { > + u64 tmp = NSEC_PER_SEC; > + do_div(tmp, oa_period); > + oa_freq_hz = tmp; > + } else > + oa_freq_hz = 0; > + > + if (oa_freq_hz > i915_oa_max_sample_rate && > + !capable(CAP_SYS_ADMIN)) { > + DRM_ERROR("OA exponent would exceed the max > sampling frequency (sysctl dev.i915.oa_max_sample_rate) %uHz without root > privileges\n", This line is getting a little too long.
Reviewed-by: Matthew Auld <matthew.a...@intel.com> _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx