[jira] Updated: (HARMONY-6039) Implement on-demand class library parsing to avoid unnecessary jar/zip parsing during startup

["Wenlong Li (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HARMONY-6039?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wenlong Li updated HARMONY-6039:
--------------------------------

    Attachment: on_demand_patch

We introduce another property file, which defines mappting between module and its class library. These info is extracted from the manifest in each module.
btw, On-demand jar parsing doesn't affect the modularity feature of Harmony. 

> Implement on-demand class library parsing to avoid unnecessary jar/zip parsing during startup
> ---------------------------------------------------------------------------------------------
>
>                 Key: HARMONY-6039
>                 URL: https://issues.apache.org/jira/browse/HARMONY-6039
>             Project: Harmony
>          Issue Type: Improvement
>          Components: VM
>         Environment: Conduct experiments on Windows XP, Core 2 Quad-core machine
>            Reporter: Wenlong Li
>         Attachments: on_demand_patch
>
>
> During VM creation, Harmony will parse all class libraried defined in bootclasspath.properties under jre/lib/boot directory. However, not all class libraries are accessed during startup. That means, it is not necessary to open and resolve all these class libraries.
> In this patch, we implement the on-demand jar parsing. We leverage the class library info defined in the manifest file of each module. For a request class, if it is not available in existing class table, we then parse its class library info, and check which module contains this requested class. That is, we parse the class library on demand.
> Using on-demand class library parsing, we can reduce the VM creation time from 20+ seconds to 3 seconds.
> We enable this feature into reading boot class path option, and it can be disabled by using -Xbootclasspath option. 

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