Re: [PATCH] P4 events utm_mandatory

[Philippe E. <ph...@wa...>]

graydon hoare wrote:
> On Wed, 2003-01-15 at 16:53, William Cohen wrote:
> 
> 
>>Making some of these things manditory isn't the right thing to do.
> 
> 
> well, perhaps. I'm not entirely clear on the semantics of some of these
> things, to be honest. for example, as you say, there is only one bit
> defined as a mask value for LOAD_PORT_REPLAY: split load. so, clearly if
> I set that bit to 1, I'll be recording the split-load replays.
> 
> but I wonder: if I set that bit to 0, does that mean I'm going to record
> non-split-load replays? or am I going to record nothing at all? if the
> former, then certainly making it utm_mandatory is wrong; if the latter,
> I don't see what the harm is.

Same problem occur for:


  /* MISPRED_BRANCH_RETIRED */
  static struct op_unit_mask um_mispred_branch_retired =
-    {1, utm_bitmask, 0x01, +    {1, utm_mandatory, 0x01,       { {0x01, 
"retired instruction is non-bogus"} } };

does this means than 0 count bogus instruction and there
is no way to count bogus and non-bogus retired insn or
only non-bogus insn can be counted ? If not utm_mandatory
is required. If the documentation is not enough clear test
are needed.

Anyway for unit mask with only one bit allowed utm_bitmask
is always wrong: if the bit is required utm_mandatory is
needed else utm_exclusive must be used and unit mask == 0
allowed explicitely.

so on:

  static struct op_unit_mask um_mispred_branch_retired =
     {1, utm_bitmask, 0x01, +    {1, utm_mandatory, 0x01,       { {0x01, 
"retired instruction is non-bogus"} } };

or

  static struct op_unit_mask um_mispred_branch_retired =
     {2, utm_excelusive, 0x01, +    {1, utm_mandatory, 0x01,
        { {0x01, "retired instruction is non-bogus"},
          {0x00, bogus (or non bogus and bogus ?)"}  } };

libop/op_events.c:

int op_check_unit_mask(struct op_unit_mask const * allow, u16 um)
...

	case utm_bitmask:
		// Must reject 0 bit mask because it can count nothing
		if (um == 0)
			break;
...
return -1;

regards,
Phil