RFR: 8378675: PPC64: increase instruction cache line size [v2]

[Richard Reingruber]

On Wed, 25 Feb 2026 14:56:15 GMT, David Briemann <dbriemann at openjdk.org> wrote:

>> Set the instruction cache line size for Power to 128 bytes.
>> 
>> Add functions to retrieve the data cache line size and instruction cache line size from the system (AIX & Linux).
>
> David Briemann has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - add comments that explain getconf behavior
>  - update copyright headers

src/hotspot/os/linux/os_linux.cpp line 5389:

> 5387:   int size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
> 5388:   // On some Linuxes this is not available, then return DEFAULT_CACHE_LINE_SIZE.
> 5389:   return (size == 0) ? DEFAULT_CACHE_LINE_SIZE : size;

Suggestion:

  return (size <= 0) ? DEFAULT_CACHE_LINE_SIZE : size;

The man page says that sysconf returns -1 on error (e.g. if the queried name is unknown).

src/hotspot/os/linux/os_linux.cpp line 5396:

> 5394:   int size = sysconf(_SC_LEVEL1_ICACHE_LINESIZE);
> 5395:   // On some Linuxes this is not available, then return DEFAULT_CACHE_LINE_SIZE.
> 5396:   return (size == 0) ? DEFAULT_CACHE_LINE_SIZE : size;

Suggestion:

  return (size <= 0) ? DEFAULT_CACHE_LINE_SIZE : size;

The man page says that sysconf returns -1 on error (e.g. if the queried name is unknown).

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PR Review Comment: https://git.openjdk.org/jdk/pull/29918#discussion_r2857712624
PR Review Comment: https://git.openjdk.org/jdk/pull/29918#discussion_r2857712860