On Fri, 24 Oct 2025 08:25:21 GMT, Kieran Farrell <[email protected]> wrote:
> Currently, it is only possible to read the number of open file descriptors of > a Java process via the `UnixOperatingSystemMXBean` which is only accessible > via JMX enabled tools. To improve servicability, it would be benifical to be > able to view this information from jcmd VM.info output or hs_err_pid crash > logs. This could help diagnose resource exhaustion and troubleshoot "too many > open files" errors in Java processes on Unix platforms. > > This PR adds reporting the current open file descriptor count to both jcmd > VM.info output or hs_err_pid crash logs by refactoring the native JNI logic > from > `Java_com_sun_management_internal_OperatingSystemImpl_getOpenFileDescriptorCount0` > of the `UnixOperatingSystemMXBean` into hotspot. Apple's API for retrieving > open file descriptor count provides an array of the actual FDs to determine > the count. To avoid using `malloc` to store this array in a potential signal > handling context where stack space may be limited, the apple implementation > instead allocates a fixed 32KB struct on the stack to store the open FDs and > only reports the result if the struct is less than the max (1024 FDs). This > should cover the majoirty of use cases. This pull request has now been integrated. Changeset: b0831572 Author: Kieran Farrell <[email protected]> Committer: Thomas Stuefe <[email protected]> URL: https://git.openjdk.org/jdk/commit/b0831572e2cd9dbff9ee2abcdf81a493ddcecc7e Stats: 106 lines in 8 files changed: 105 ins; 1 del; 0 mod 8359706: Add file descriptor count to VM.info Reviewed-by: kevinw, stuefe ------------- PR: https://git.openjdk.org/jdk/pull/27971
