8008290: (profiles) Startup regression due to additional checking of JAR file manifests
iris.clark at oracle.com
Thu Feb 21 16:42:08 UTC 2013
Just curious. How are you testing startup? Custom micro benchmark or are you using something else?
From: Alan Bateman
Sent: Thursday, February 21, 2013 6:33 AM
Subject: 8008290: (profiles) Startup regression due to additional checking of JAR file manifests
This one is a startup-time regression caused by the compact profiles work.
As background, there was a lot of work done in the distant past on startup performance. Amongst the startup improvements was to the code that checks for the Class-Path attribute when opening JAR files so that it skips checking of known JAR files (in the JDK) and in addition do a quick search of the manifest to avoid parsing it when not present. These optimizations were disrupted by the profiles work so the change here is to fix this regression to get startup performance back to where it was previously.
The changes are very simple, it just extends the implementation to check for the Profile attribute in the same way that we've always checked the Class-Path attribute. I've also refreshed the list of "known" JAR files as that has been stale for some time. The changes do mean the manifest bytes are searched twice and it might benefit from using a multi-pattern search and that it something for another day. So far, at least in the startup tests that I've run, it doesn't make any observable difference and startup performance is back to where it was.
The webrev with the changes is here. I should point out that this is against jdk8/build as the changes aren't in jdk8/tl at this time.
Finally, I should explain that the goal here is simply to get startup back to where it was. There is clearly other clean-up that should be done on this code at some point.
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