On Thursday, June 9, 2016 10:00:40 AM PDT Ilia Mirkin wrote:
> On Jun 9, 2016 4:10 AM, "Kenneth Graunke" <kenn...@whitecape.org> wrote:
> >
> > Skylake changes the representation of shared local memory size:
> >
> > Size | 0 kB | 1 kB | 2 kB | 4 kB | 8 kB | 16 kB | 32 kB | 64 kB |
> > -------------------------------------------------------------------
> > Gen7-8 | 0 | none | none | 1 | 2 | 3 | 4 | 5 |
> > -------------------------------------------------------------------
> > Gen9+ | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
> >
> > The old formula would substantially underallocate the amount of space.
> > This fixes GPU hangs on Skylake when running with full thread counts.
> >
> > Cc: "12.0" <mesa-sta...@lists.freedesktop.org>
> > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> > ---
> > src/mesa/drivers/dri/i965/gen7_cs_state.c | 15 ++++++++++-----
> > 1 file changed, 10 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/gen7_cs_state.c
> b/src/mesa/drivers/dri/i965/gen7_cs_state.c
> > index 750aa2c..aff1f4e 100644
> > --- a/src/mesa/drivers/dri/i965/gen7_cs_state.c
> > +++ b/src/mesa/drivers/dri/i965/gen7_cs_state.c
> > @@ -150,11 +150,16 @@ brw_upload_cs_state(struct brw_context *brw)
> > assert(prog_data->total_shared <= 64 * 1024);
> > uint32_t slm_size = 0;
> > if (prog_data->total_shared > 0) {
> > - /* slm_size is in 4k increments, but must be a power of 2. */
> > - slm_size = 4 * 1024;
> > - while (slm_size < prog_data->total_shared)
> > - slm_size <<= 1;
> > - slm_size /= 4 * 1024;
> > + /* Shared Local Memory Size is specified as powers of two. */
> > + slm_size = util_next_power_of_two(prog_data->total_shared);
> > +
> > + if (brw->gen >= 9) {
> > + /* Use a minimum of 1kB; turn an exponent of 10 (1024 kB) into
> 1. */
> > + slm_size = ffs(MAX2(slm_size, 1024)) - 10;
> > + } else {
> > + /* Use a minimum of 4kB; convert to the pre-Gen9
> representation. */
> > + slm_size = MAX2(slm_size, 4096) / 4096;
>
> According to your chart, 16k should end up with 3, but this logic will
> produce 4. The old comment said it was in increments of 4k, so I'm guessing
> just the chart needs to be adjusted.Yikes, sorry! A wrong chart is better than no chart at all. I meant: Size | 0 kB | 1 kB | 2 kB | 4 kB | 8 kB | 16 kB | 32 kB | 64 kB | ------------------------------------------------------------------- Gen7-8 | 0 | none | none | 1 | 2 | 4 | 8 | 16 | ------------------------------------------------------------------- Gen9+ | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | I should probably move this code to a helper function and put the (correct) table in a comment...
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