JDK-8330181 : Move PcDesc cache from nmethod header
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 23
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2024-04-12
  • Updated: 2024-04-29
  • Resolved: 2024-04-25
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JDK 23
23 masterFixed
Related Reports
Relates :  
JDK-8331087 - Move immutable nmethod data from CodeCache
Relates :  
JDK-8329433 - Reduce nmethod header size
Relates :  
JDK-8321944 - [premain] C1: assert(initial_pc_desc->pc_offset() < 0) failed: must be sentinel w/ -XX:CacheDataStore on linux-aarch64
Relates :  
JDK-8331012 - Undo JDK-8304725 changes after JDK-8330181
Description
Currently PcDescCache  (32 bytes: PcDesc* _pc_descs[4]) is allocated in `nmethod` header.

Investigate possibility to move it to C heap similar to ExceptionCache to reduce size of `nmethod` header and remove WXWrite transition when we update the cache in `PcDescCache::add_pc_desc()`

Main concern is performance because we will add one pointer load to each query.
Comments
Changeset: b3bcc494 Author: Vladimir Kozlov <kvn@openjdk.org> Date: 2024-04-25 22:46:11 +0000 URL: https://git.openjdk.org/jdk/commit/b3bcc49491b8f8ad337eb4c06201a5468e5c1159
25-04-2024
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/18895 Date: 2024-04-22 16:54:40 +0000
22-04-2024