On Wed, 10 Sep 2025 21:51:38 GMT, David Beaumont <[email protected]> wrote:
> Summary: Add two new methods to ImageReader to make SystemModuleReader more > performant. > > Analysis of benchmarks shows that when the vast majority of resources > (~11,000 in the Perfstartup-SwingSet-G1 benchmark) tested for in > SystemModuleReader do NOT exist, performance is degraded compared to this > code prior to the refactoring in JDK-8360037. > > The current refactoring of ImageReader has everything going through a single > "findNode()" method for simplest possible encapsulation, but while this is > functionally correct, it's not tuned for testing for the non-existence of > resources. > > In particular: > 1. SystemModuleReader only requests resources (i.e. things in the jimage file > with paths *not* starting /modules/ or /packages/). This means findNode() > does two look-ups for the resource, the first of which will always fail. > 2. The containsResource() logic doesn't need to create and cache nodes in > ImageReader, it can just check for the presence of an ImageLocation > corresponding to a resource. > > Thus two new methods are added to resolve these cases: > * findResourceNode(module, path) > * containsResource(module, path) > > Their API takes module and path separately so as to not be confusable with > findNode(nodename). > > However care must be taken to prevent these methods being fooled into > returning non-resource entries (this was possible before the refactoring by > using module names like "modules" or "packages") so new tests have been added. This pull request has now been integrated. Changeset: 9949ee31 Author: David Beaumont <[email protected]> Committer: Chen Liang <[email protected]> URL: https://git.openjdk.org/jdk/commit/9949ee3163a31f6f3c13c4fe34e8c0166210719e Stats: 175 lines in 4 files changed: 153 ins; 13 del; 9 mod 8367005: ImageReader refactor caused performance regressions for startup and footprint Reviewed-by: alanb, rriggs, jpai ------------- PR: https://git.openjdk.org/jdk/pull/27203
