RFR: 8356595: Convert -Xlog:cds to -Xlog:aot [v4]

[Ioi Lam]

On Wed, 14 May 2025 03:55:22 GMT, David Holmes <dholmes at openjdk.org> wrote:

> But given you state that CDS is a subset of AOT - the AOT for metaspace - does it really make sense to simply rebadge "cds" logging as "aot"? It seems to me that "aot" logging will generate massive amounts of data if everything AOT related logs when "aot" is used. Would you not want finer-grained logging such that "cds" becomes "aot+metaspace" as described?

Many "cds" logs already have sub-levels. E.g., `[cds][heap]`, `[cds][module]`. The top-level `[cds]` log are used for general trouble shooting (e.g, the CDS archive cannot be mapped). Today, if you run with -Xlog:cds, there's a fair amount of logs but not massive:


$ java -Xlog:cds --version 
[0.003s][info][cds] trying to map /jdk3/bld/tin/images/jdk/lib/server/classes.jsa
[0.003s][info][cds] Opened shared archive file /jdk3/bld/tin/images/jdk/lib/server/classes.jsa.
[0.003s][info][cds] The shared archive file was created with UseCompressedOops = 1, UseCompressedClassPointers = 1, UseCompactObjectHeaders = 0
[0.003s][info][cds] Core region alignment: 4096
[0.003s][info][cds] ArchiveRelocationMode: 1
[0.003s][info][cds] ArchiveRelocationMode == 1: always map archive(s) at an alternative address
[0.003s][info][cds] Try to map archive(s) at an alternative address
[0.003s][info][cds] Reserved archive_space_rs [0x000073d7fa000000 - 0x000073d7fb000000] (16777216) bytes (includes protection zone)
[0.003s][info][cds] Reserved class_space_rs   [0x000073d7fb000000 - 0x000073d83b000000] (1073741824) bytes
[0.003s][info][cds] Mapped static  region #0 at base 0x000073d7fa001000 top 0x000073d7fa48b000 (ReadWrite)
[0.003s][info][cds] Mapped static  region #1 at base 0x000073d7fa48b000 top 0x000073d7fad37000 (ReadOnly)
[0.003s][info][cds] Mapped static  region #2 at base 0x000073d88b5ce000 top 0x000073d88b600000 (Bitmap)
[0.005s][info][cds] archived module property jdk.module.main: (null)
[0.005s][info][cds] archived module property jdk.module.addexports: (null)
[0.005s][info][cds] archived module property jdk.module.addmods: (null)
[0.005s][info][cds] archived module property jdk.module.enable.native.access: (null)
[0.005s][info][cds] archived module property jdk.module.addopens: (null)
[0.005s][info][cds] optimized module handling: enabled
[0.005s][info][cds] full module graph: enabled
[0.005s][info][cds] CDS archive was created with max heap size = 128M, and the following configuration:
[0.005s][info][cds]     narrow_klass_base at mapping start address, narrow_klass_pointer_bits = 32, narrow_klass_shift = 0
[0.005s][info][cds]     narrow_oop_mode = 0, narrow_oop_base = 0x0000000000000000, narrow_oop_shift = 0
[0.005s][info][cds] The current max heap size = 15488M, G1HeapRegion::GrainBytes = 8388608
[0.005s][info][cds]     narrow_klass_base = 0x000073d7fa000000, arrow_klass_pointer_bits = 32, narrow_klass_shift = 0
[0.005s][info][cds]     narrow_oop_mode = 1, narrow_oop_base = 0x0000000000000000, narrow_oop_shift = 3
[0.005s][info][cds]     heap range = [0x0000000438000000 - 0x0000000800000000]
[0.005s][info][cds] Preferred address to map heap data (to avoid relocation) is 0x00000000ffe00000
[0.005s][info][cds] Heap data mapped at 0x00000007ff800000, size =  1157176 bytes
[0.005s][info][cds] CDS heap data relocation delta = 30058479616 bytes
[0.005s][info][cds] use_full_module_graph = true; java.base = 0x000073d7fa4860a8
[0.005s][info][cds] patching heap embedded pointers: narrowOop 0xffe00000 -> 0xfff00000
[0.005s][info][cds] CDS heap data quick relocation not possible
[0.005s][info][cds] Unmapping region #2 at base 0x000073d88b5ce000 (Bitmap)


Going forward, we may change some of the logs to add an extra level if it makes sense. At this point, I don't see any logs that need immediate attention:


$ java -Xlog:logging=debug
[....]
[0.009s][debug][logging] Available tag sets: , aot, aot+class, aot+codecache, aot+codecache+exit, aot+codecache+init, aot+codecache+reloc, aot+codecache+stringtable, aot+codecache+stubs, aot+hashtables, aot+heap, aot+heap+mirror, aot+init, aot+jvmti, aot+lambda, aot+link, aot+load, aot+mirror, aot+ref, aot+reloc, aot+unshareable, arguments, attach, cds, cds+class, cds+dynamic, cds+hashtables, cds+init, cds+lambda, cds+map, cds+map+oops, cds+module, cds+reloc, cds+resolve, cds+verification, cds+vtables,


> I'm undecided whether this aspect of the work requires a CSR request ... but it never hurts to have one. Obviously in 26 there will be one for the actual deprecation/obsoletion/expiration process.

Since most of the logs are for diagnostic purposes and are often changed along with the VM code, I think it's not necessary for a CSR.

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PR Comment: https://git.openjdk.org/jdk/pull/25136#issuecomment-2880887150