harmony-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Regis <xu.re...@gmail.com>
Subject [classlib] performance of java.io.File
Date Wed, 11 Mar 2009 08:49:42 GMT
Hi all,

Recently I found our java.io.File implementation is obviously slower 
than RI on Windows, especially when a SecurityManager is installed.

Testing with following simple test case:

         File file = new File("FilePerTest.java");
         long start = System.currentTimeMillis();
         for (int i = 0; i < 40000; ++i) {
         long end = System.currentTimeMillis();

hy without SecuirtyManager	ri without SecuirtyManager
6766ms				1203ms

after installing a SecuirtyManager
System.setSecurityManager(new SecurityManager());

hy with SecuirtyManager		ri with SecuirtyManager
54406ms				4078ms

We can see the gap is huge. After some investigations, I found two 
problems in Harmony implemenation:

1. Harmony used File.getCanonicalPath() in FilePermission, which is very 
slow. Because if a SecurityManager was installed, every file operation 
would be check by FilePermission, that cause the huge gap (54406ms 
compare to 4078ms).

2. in file native code file.c, ioh_convertToPlatform is called by every 
method which "convert all separators to the proper platform separator 
and remove duplicates on non POSIX platforms." (copied from comment of 
method), that is exactly what File.fixSlashes did, I think they are 

I have created a JIRA HARMONY-6116 to track this issue, and sub-task 
HARMONY-6117 for 1. A prototype patch already attach to HARMONY-6117, 
your comments and suggestions are welcome.

Best Regards,

View raw message