On Thu, May 08, 2014 at 08:53:38AM -0700, Volkin, Bradley D wrote: > On Thu, May 08, 2014 at 06:15:44AM -0700, Lespiau, Damien wrote: > > On Thu, May 08, 2014 at 02:05:07PM +0100, Damien Lespiau wrote: > > > On Mon, Apr 28, 2014 at 08:22:08AM -0700, bradley.d.volkin@xxxxxxxxx wrote: > > > > From: Brad Volkin <bradley.d.volkin@xxxxxxxxx> > > > > +/* > > > > + * Different command ranges have different numbers of bits for the opcode. > > > > + * In order to use the opcode bits, and only the opcode bits, for the hash key > > > > + * we should use the MI_* command opcode mask (since those commands use the > > > > + * fewest bits for the opcode.) > > > > + */ > > > > +#define CMD_HASH_MASK STD_MI_OPCODE_MASK > > > > > > This is not very convicing (but could well be correct). > > > > > > #define STD_MI_OPCODE_MASK 0xFF800000 > > > #define STD_3D_OPCODE_MASK 0xFFFF0000 > > > > > > So it only works if the 3D opcodes have the top 9 bits all distinct? > > > > To expand on that, with the attached program: > > > > $ ./minimal-hash-hsw-render | wc -l > > 44 > > > > $ ./minimal-hash-hsw-render | sort -u | wc -l > > 37 > > Yes, as it's currently written, some commands may hash to the same > bucket. The per-bucket search will use the full mask from the cmd > descriptor to get an exact match. > > The issue is that, for example, MI commands in a batch may use bits > 22:16 for something other than the opcode (e.g. GGTT vs PPGTT). If we > mask a command from a batch with 0xFFFF0000 then an MI command may hash > to the wrong bucket. If we want a perfect hash then I suppose we should > look at bits 31:29 and mask with the exact STD_xx_OPCODE_MASK for the > client. The existing INSTR_CLIENT_MASK/SHIFT defines could be reused > for that. Ah that works then, not super convinced that's the best way we can do it, but it seems to be an improvement, so well... can't argue with that. -- Damien _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
