Re: [RFC] perf: EBNF for event syntax

[Lin Ming <ming.m.lin@intel.com>]

On Fri, 2011-03-25 at 19:07 +0800, Peter Zijlstra wrote:
> On Wed, 2011-03-23 at 11:36 +0800, Lin Ming wrote:
> > Hi, all
> > 
> > On Thu, Mar 17, 2011 at 2:02 AM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > > How about we start writing proper EBNF syntax rules for this stuff, its
> > > getting seriously out of hand.
> > http://marc.info/?l=linux-kernel&m=130029871318866&w=2
> > 
> > As Peter suggested, I wrote a simple EBNF for event syntax, as below.
> > My first plan is to pass in extra config value for some events,
> > for example, offcore response and load latency.
> > 
> > perf record -e r100b(0004):p
> > 
> > As above, the extra config value 0004 is passed in the parentheses.
> > 
> > The EBNF
> > ========
> > 
> > EventList		:=	Event [',' EventList]
> 
> There was a suggestion a while back to make:
> 
>  -e ev1,ev2,ev3
> 
> create an event group with ev2 and ev3 siblings of ev1, and have
> multiple -e instances create separate counters.
> 
> The problem is that its not backwards compatible, but something like
> that would still be very nice to have.

Currently, it means a list of independent events, right?

> 
> > Event			:= 	HardwareEvent 		|
> > 				RawEvent		|
> > 				SoftwareEvent		|
> > 				TracepointEvent		|
> > 				HardwareBreakpointEvent
> > 
> > HardwareEvent		:=	HardwareEventName [ExtraConfig] [Modifer]
> > HardwareEventName	:=	'cpu-cycles' | 'cycles' | 'instructions' /* and so on ...*/
> > ExtraConfig		:=	'(' ConfigValue [',' ConfigValue] ')'
> > ConfigValue		:=	HexNumber
> > 
> > RawEvent		:=	RawSeperator RawCode [ExtraConfig] [Modifer]
> > RawSeperator		:=	'r'
> > RawCode			:=	HexNumber
> > 
> > SoftwareEvent		:=	SoftwareEventName
> > SoftwareEventName	:=	'cpu-clock' | 'task-clock' | 'faults' /* and so on ...*/
> > 
> > TracepointEvent		:=	SubsystemName ':' TracepointName
> > SubsystemName		:=	/* All AsciiString except the pre-defined hardware/software/cache events name and BreakpointSeparator */
> > TracepointName		:=	'*' | AsciiString
> > 
> > HardwareBreakpointEvent	:=	BreakpointSeparator BreakpointAddress [':' AccessType]
> > BreakpointSeparator	:=	'mem:'
> > BreakpointAddress	:=	HexNumber
> > AccessType		:=	'r' | 'w' | 'x'
> > 
> > Modifier		:= 	ModifierSperator ModifierList
> > ModifierSperator	:= 	':'
> > ModifierList		:= 	ModifierItem ModifierList
> > ModifierItem		:= 	{PreciseModifer} | kernelModifer | UserModifer | HypervisorModifer
> > PreciseModifer		:= 	'p' /* Can be multiple PreciseModifers */
> > kernelModifer		:= 	'k'
> > UserModifer		:= 	'u'
> > HypervisorModifer	:= 	'h'
> 
> Otherwise, very nice. Eventually we'll be able to use a parser generator
> for this.

Yes, bison/yacc is good for this.