8010309 : PlatformLogger: isLoggable performance / waste due to HashMap<Integer, Level (original) (raw)

Mandy Chung mandy.chung at oracle.com
Tue Mar 26 21:37:59 UTC 2013

Hi Peter,

http://dl.dropbox.com/u/101777488/jdk8-tl/PlatformLogger/webrev.08/index.html I'm glad that you observe similar performance improvement without the need of method handles. I reviewed this version and realize that the map from j.u.l.Level object to LevelEnum can be removed entirely.

sun.util.logging.PlatformLogger is an internal API that should only be used by JDK. The static final int fields representing the level value can be changed to be static final LevelEnum type instead. I checked the JDK code that uses PlatformLogger and no code will be impacted by the change of the type of these static fields. So it removes the need to map from an integer value to LevelEnum. Mapping from a j.u.l.Level to LevelEnum is trivial - the name of the LevelEnum is the same as j.u.l.Level (e.g. LevelEnum.FINEST and Level.FINEST), you can call LoggingSupport.getLevelName(javaLevel) to find its name and LevelEnum.valueOf(levelName) returns the LevelEnum instance. However, this would require more changes - basically the methods taking "int level" as a parameter would be modified to take LevelEnum and getLevel() would return LevelEnum too. I think it's worth doing this cleanup to get rid of the unnecessary conversion from int -> enum -> j.u.l.Level and vice versa. I also recommend to rename LevelEnum to Level which is an inner class of PlatformLogger. What do you think of this alternative to get rid of the map?

Some other comments of your patch:

Have you tried: Class.forName("sun.util.logging.PlatformLogger.JavaLoggerProxy", false, PlatformLogger.getClassLoader());

would this give you the same performance improvement? If so, you can keep the static initialization in the JavaLoggerProxy class.

Thanks for expanding the PlatformLoggerTest to cover additional test cases. It's good that you compare the value of the PlatformLogger static final fields with j.u.l.Level.intValue(). You now can use the API to compare the LevelEnum with Level rather than reflection. Perhaps you can add the getName() and intValue() methods in LevelEnum class (just a thought).

Mandy

On 3/25/13 9:31 AM, Peter Levart wrote:

Well, Laurent, Mandy,

It turns out that the dispatch speed-up (or lack of slow-down to be precise) is possible without MethodHandles too. Maybe some VM guru could shed some light on this, but the following is currently the fastest variant: http://dl.dropbox.com/u/101777488/jdk8-tl/PlatformLogger/webrev.08/index.html What I did is a simple "if" deciding between two call-sites, making sure that each is only dispatching to single class. This only works, if both classes (LoggerProxy and JavaLoggerProxy) are loaded in advance, before 1st invocation on any of them is made (might be that using MethodHandles forced initialization of both classes beforehand and hence the speed-up). If I don't load JavaLoggerProxy before warming-up with LoggerProxy, then when j.u.logging is enabled, speed drops for a factor of almost 4 and never catches up even after very long time. This pre-loading also helps for a normal single call site dispatch that dispatches to two distinct classes, but the speed 1st drops when the class changes, and only catches-up after several billions of iterations (30s tight loop on i7). Now, because JavaLoggerProxy is initialized early, I had to move the initialization of j.u.logging.Level objects and mappings to a separate class "JavaLevel". Here are the benchmark results for this last iteration...

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