On Jun 9, 2016 1:10 AM, "Kenneth Graunke" <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>> 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" <<a href="mailto:mesa-stable@lists.freedesktop.org">mesa-stable@lists.freedesktop.org</a>> > Signed-off-by: Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>> > --- > 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; Are you sure you don't want ffs in both cases? The table above really looks like powers of two all around. const unsigned slm_divisor = brw->gen >= 9 ? 1024 : 4096; slm_size = DIV_ROUND_UP(prog_data->total_shared, slm_divisor); slm_size = util_next_power_of_two(slm_size); slm_size = ffs(slm_size); You may be also be able to replace the last two lines with a clever use of clz. If the table in the commit message comes from the bspec, it might be good to put it here as a comment. > + } > } > > desc[dw++] = > -- > 2.8.3 > > _______________________________________________ > mesa-dev mailing list > <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> > <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a>