RFR: 8324580: SIGFPE on THP initialization on kernels < 4.10 [v6]

[Zdenek Zambersky]

> **Problem:**
> When THP is enabled, JDK reads `/sys/kernel/mm/transparent_hugepage/hpage_pmd_size` file to [detect](https://github.com/openjdk/jdk/blob/96607df7f055a80d56ea4c19f3f4fcb32838b1f8/src/hotspot/os/linux/hugepages.cpp#L206) large page size. However this file only [appeared](https://github.com/torvalds/linux/commit/49920d28781dcced10cd30cb9a938e7d045a1c94) in kernel 4.10 and does not exist on kernel old kernels (such as 3.10 used by RHEL-7).
> 
> This results in detected large page size of 0B and crash, when `-XX:+UseTransparentHugePages` is used on old kernel.
> 
> gdb --args jdk-23+6/bin/java -XX:+UseTransparentHugePages -Xmx128m -Xlog:pagesize -version
> ...
> [0.005s][info][pagesize] Static hugepage support:
> [0.005s][info][pagesize]   hugepage size: 2M
> [0.005s][info][pagesize]   hugepage size: 1G
> [0.005s][info][pagesize]   default hugepage size: 2M
> [0.005s][info][pagesize] Transparent hugepage (THP) support:
> [0.005s][info][pagesize]   THP mode: always
> [0.005s][info][pagesize]   THP pagesize: 0B
> [0.005s][info][pagesize] Shared memory transparent hugepage (THP) support:
> [0.005s][info][pagesize]   Shared memory THP mode: unknown
> [0.005s][info][pagesize] JVM will attempt to prevent THPs in thread stacks.
> [0.005s][info][pagesize] UseLargePages=1, UseTransparentHugePages=1
> [0.005s][info][pagesize] Large page support enabled. Usable page sizes: 4k. Default large page size: 0B.
> 
> Program received signal SIGFPE, Arithmetic exception.
> [Switching to Thread 0x7ffff7fc2700 (LWP 31385)]
> 0x00007ffff68eeb20 in lcm(unsigned long, unsigned long) () from /home/tester/jdk-23+6/lib/server/libjvm.so
> (gdb) bt
> #0  0x00007ffff68eeb20 in lcm(unsigned long, unsigned long) () from /home/tester/jdk-23+6/lib/server/libjvm.so
> #1  0x00007ffff64a68f2 in Arguments::apply_ergo() () from /home/tester/jdk-23+6/lib/server/libjvm.so
> #2  0x00007ffff700458f in Threads::create_vm(JavaVMInitArgs*, bool*) () from /home/tester/jdk-23+6/lib/server/libjvm.so
> #3  0x00007ffff6a2373f in JNI_CreateJavaVM () from /home/tester/jdk-23+6/lib/server/libjvm.so
> #4  0x00007ffff7fe704b in InitializeJVM (ifn=<synthetic pointer>, penv=0x7ffff7fc1ea8, pvm=0x7ffff7fc1ea0) at src/java.base/share/native/libjli/java.c:1550
> #5  JavaMain (_args=<optimized out>) at src/java.base/share/native/libjli/java.c:491
> #6  0x00007ffff7feb1c9 in ThreadJavaMain (args=<optimized out>) at src/java.base/unix/native/libjli/java_md.c:650
> #7  0x00007ffff7bc6ea5 in start_thread (arg=0x7ffff7fc2700) at pthread_create.c:307
> #8  0x00007ffff76ebb0d ...

Zdenek Zambersky has updated the pull request incrementally with one additional commit since the last revision:

  Moved fallback logic of THP pagesize computation into HugePages class

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/17545/files
  - new: https://git.openjdk.org/jdk/pull/17545/files/72046689..ea2e136c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17545&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17545&range=04-05

  Stats: 31 lines in 3 files changed: 16 ins; 14 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17545.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17545/head:pull/17545

PR: https://git.openjdk.org/jdk/pull/17545