RFR: 8330584: IGV: XML does not save all node properties

[Roberto Castañeda Lozano]

On Mon, 6 May 2024 12:06:20 GMT, Tobias Holenstein <tholenstein at openjdk.org> wrote:

> When C2 sends graphs over the network to IGV, each graph is sent separately. The same applies if C2 saves graphs to XML: each graph is saved with all it's nodes as a separate `<graph>...</graph>` in the XML
> 
> To save space, graphs that are saved from IGV only contains the incremental difference for each graph. This saves a lot of space (~5-10x). The logic happens in Printer.java -> `exportInputGraph(.., difference=true, ...)` Unfortunately, there is a bug in this logic: the properties of the nodes are not saved correctly. 
> 
> [graphs.zip](https://github.com/openjdk/jdk/files/15220940/graphs.zip) contains 4 graphs: 
> 
> `graph_c2.xml` (230KB) - a XML saved from C2 
> `graph_igv_bug.xml` (73KB) - opened `graph_c2.xml` in IGV (without this fix) and save as `graph_igv_bug.xml`.
> `graph_igv_fixed.xml` (123KB) - opened `graph_c2.xml` in IGV (with this fix) and save as `graph_igv_fixed.xml `.
> 
> As you can see `graph_igv_fixed.xml` is twice as large as `graph_igv_bug.xml` because it contains the missing properties. But now the memory saving from the original `graph_c2.xml` is only ~2x. 
> Therefore a new format for saving is added: graphs can now be saved and opened from IGV as `.igv`. This uses a compressed (ZIP) format. 
> 
> `graph.igv` (10KB) is the same graph as `graph_c2.xml` (230KB). But it uses difference graph compression and ZIP compression and is in total 23x smaller in memory footprint. 
> 
> 
> 
> E.g. The root in the last graph of difference_true.xml has way less properties than in difference_false.xml.

Good catch and nice feature!

src/utils/IdealGraphVisualizer/Coordinator/src/main/java/com/sun/hotspot/igv/coordinator/OutlineTopComponent.java line 578:

> 576:             SwingUtilities.invokeLater(() -> {
> 577:                 for (Node child : manager.getRootContext().getChildren().getNodes(true)) {
> 578:                     // Nodes a lazily created. By expanding and collapsing they are all initialized

Suggestion:

                    // Nodes are lazily created. By expanding and collapsing they are all initialized

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Marked as reviewed by rcastanedalo (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19104#pullrequestreview-2045436896
PR Review Comment: https://git.openjdk.org/jdk/pull/19104#discussion_r1593900816