Levente Uzonyi uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-ul.904.mcz

==================== Summary ====================

Name: Kernel-ul.904
Author: ul
Time: 17 February 2015, 1:40:49.811 pm
UUID: 7e873979-7e22-4abb-bd69-fa6d72f8c7fc
Ancestors: Kernel-nice.902

Avoid the frequent time checks, and the clock rollover bug in BlockClosure >> #bench.
Introduced BlockClosure >> #benchFor:, a variant of #bench, which takes the duration of the benchmark as its parameter.
Added more information about the running times to the answer.
E.g.:

[ 10 factorial ] benchFor: 0.1 seconds. "'7,990,000 per second. 125 nanoseconds per run.'"
[ 100 factorial ] benchFor: 10 seconds. "'19,900 per second. 50.3 microseconds per run.'"
[ 1000 factorial ] bench. "'378 per second. 2.65 milliseconds per run.'"
[ 20000 factorial ] bench. "'0.843 per second. 1.19 seconds per run.'"

=============== Diff against Kernel-nice.902 ===============

Item was changed:
  ----- Method: BlockClosure>>bench (in category 'evaluating') -----
  bench
  	"See how many times I can value in 5 seconds.  I'll answer a meaningful description."
  
+ 	^self benchFor: 5 seconds!
- 	| startTime endTime count roundTo3Digits |
- 	roundTo3Digits := [:num |
- 		| rounded lowDigit |
- 		rounded := (num * 1000) rounded. "round to 1/1000"
- 		lowDigit := (rounded numberOfDigitsInBase: 10) - 3. "keep only first 3 digits"
- 		rounded := rounded roundTo:(10 raisedTo: lowDigit).
- 		(lowDigit >= 3 or: [rounded \\ 1000 = 0]) "display fractional part only when needed"
- 			ifTrue: [(rounded // 1000) asStringWithCommas]
- 			ifFalse: [(rounded / 1000.0) printString]].
- 	count := 0.
- 	endTime := Time millisecondClockValue + 5000.
- 	startTime := Time millisecondClockValue.
- 	[ Time millisecondClockValue > endTime ] whileFalse: [ self value.  count := count + 1 ].
- 	endTime := Time millisecondClockValue.
- 	^count = 1
- 		ifTrue: [ (roundTo3Digits value: (endTime - startTime) / 1000) , ' seconds.' ]
- 		ifFalse:
- 			[ (roundTo3Digits value: (count * 1000) / (endTime - startTime)) , ' per second.' ]!

Item was added:
+ ----- Method: BlockClosure>>benchFor: (in category 'evaluating') -----
+ benchFor: aDuration
+ 	"See how many times I can value within the given duration.  I'll answer a meaningful description."
+ 
+ 	| startTime shouldRun count elapsedTime  roundTo3Digits delay |
+ 	roundTo3Digits := [:num |
+ 		| rounded lowDigit |
+ 		rounded := (num * 1000) rounded. "round to 1/1000"
+ 		lowDigit := (rounded numberOfDigitsInBase: 10) - 3. "keep only first 3 digits"
+ 		rounded := rounded roundTo:(10 raisedTo: lowDigit).
+ 		(lowDigit >= 3 or: [rounded \\ 1000 = 0]) "display fractional part only when needed"
+ 			ifTrue: [(rounded // 1000) asStringWithCommas]
+ 			ifFalse: [(rounded / 1000.0) printString]].
+ 	delay := aDuration asDelay.
+ 	count := 0.
+ 	shouldRun := true.
+ 	[ delay wait. shouldRun := false ] forkAt: Processor timingPriority - 1.
+ 	startTime := Time millisecondClockValue.
+ 	[ shouldRun ] whileTrue: [ 
+ 		self value.
+ 		count := count + 1 ].
+ 	elapsedTime := Time millisecondsSince: startTime.
+ 	^(roundTo3Digits value: count * 1000 / elapsedTime) , ' per second.', ((
+ 		#(
+ 			(1e-3 'seconds')
+ 			(1 'milliseconds')
+ 			(1e3 'microseconds')
+ 			(1e6 'nanoseconds')
+ 		)
+ 			detect: [ :pair | elapsedTime * pair first >= count ]
+ 			ifNone: [ #(1e9 'picoseconds') ])
+ 		in: [ :pair |
+ 			' {1} {2} per run.' format: {
+ 				(roundTo3Digits value: elapsedTime * pair first / count).
+ 				pair second } ])!