code review (round 1) for memory commit failure fix (8013057)

[David Holmes]

Hi Dan,

This looks good to me. Only minor quggestion is that in:

   warning("INFO: os::commit_memory(" PTR_FORMAT ", " SIZE_FORMAT
           ", %d) failed; errno=%d", addr, size, exec, err);

you also use strerror to output more meaningful text about the error.

Thanks,
David

On 25/05/2013 4:23 AM, Daniel D. Daugherty wrote:
> Greetings,
>
> I have a revised version of the proposed fix for the following bug:
>
>      8013057 assert(_needs_gc || SafepointSynchronize::is_at_safepoint())
>              failed: only read at safepoint
>
> Here are the (round 1) webrev URLs:
>
> OpenJDK: http://cr.openjdk.java.net/~dcubed/8013057-webrev/1-hsx25/
> Internal: http://javaweb.us.oracle.com/~ddaugher/8013057-webrev/1-hsx25/
>
> Testing:
> - Aurora Adhoc vm.quick batch for all OSes in the following configs:
>    {Client VM, Server VM} x {fastdebug} x {-Xmixed}
> - I've created a standalone Java stress test with a shell script
>    wrapper that reproduces the failing code paths on my Solaris X86
>    server. This test will not be integrated since running the machine
>    out of swap space is very disruptive (crashes the window system,
>    causes various services to exit, etc.)
>
> Gory details are below. As always, comments, questions and
> suggestions are welome.
>
> Dan
>
>
> Gory Details:
>
> The VirtualSpace data structure is built on top of the ReservedSpace
> data structure. VirtualSpace presumes that failed os::commit_memory()
> calls do not affect the underlying ReservedSpace memory mappings.
> That assumption is true on MacOS X and Windows, but it is not true
> on Linux or Solaris. The mmap() system call on Linux or Solaris can
> lose previous mappings in the event of certain errors. On MacOS X,
> the mmap() system call clearly states that previous mappings are
> replaced only on success. On Windows, a different set of APIs are
> used and they do not document any loss of previous mappings.
>
> The solution is to implement the proper failure checks in the
> os::commit_memory() implementations on Linux and Solaris. On MacOS X
> and Windows, no additional checks are needed.
>
> There is also a secondary change where some of the pd_commit_memory()
> calls were calling os::commit_memory() instead of calling their sibling
> os::pd_commit_memory(). This resulted in double NMT tracking so this
> has also been fixed. There were also some incorrect mmap)() return
> value checks which have been fixed.
>
> Just to be clear: This fix simply properly detects the "out of swap
> space" condition on Linux and Solaris and causes the VM to fail in a
> more orderly fashion with a message that looks like this:
>
> The Java process' stderr will show:
>
> INFO: os::commit_memory(0xfffffd7fb2522000, 4096, 4096, 0) failed; errno=11
> #
> # There is insufficient memory for the Java Runtime Environment to
> continue.
> # Native memory allocation (mmap) failed to map 4096 bytes for
> committing reserved memory.
> # An error report file with more information is saved as:
> # /work/shared/bugs/8013057/looper.03/hs_err_pid9111.log
>
> The hs_err_pid file will have the more verbose info:
>
> #
> # There is insufficient memory for the Java Runtime Environment to
> continue.
> # Native memory allocation (mmap) failed to map 4096 bytes for
> committing reserved memory.
> # Possible reasons:
> #   The system is out of physical RAM or swap space
> #   In 32 bit mode, the process size limit was hit
> # Possible solutions:
> #   Reduce memory load on the system
> #   Increase physical memory or swap space
> #   Check if swap backing store is full
> #   Use 64 bit Java on a 64 bit OS
> #   Decrease Java heap size (-Xmx/-Xms)
> #   Decrease number of Java threads
> #   Decrease Java thread stack sizes (-Xss)
> #   Set larger code cache with -XX:ReservedCodeCacheSize=
> # This output file may be truncated or incomplete.
> #
> #  Out of Memory Error
> (/work/shared/bug_hunt/hsx_rt_latest/exp_8013057/src/os/s
> olaris/vm/os_solaris.cpp:2791), pid=9111, tid=21
> #
> # JRE version: Java(TM) SE Runtime Environment (8.0-b89) (build
> 1.8.0-ea-b89)
> # Java VM: Java HotSpot(TM) 64-Bit Server VM
> (25.0-b33-bh_hsx_rt_exp_8013057_dcu
> bed-product-fastdebug mixed mode solaris-amd64 compressed oops)
> # Core dump written. Default location:
> /work/shared/bugs/8013057/looper.03/core
> or core.9111
> #
>
> You might be wondering why we are assuming that the failed mmap()
> commit operation has lost the 'reserved memory' mapping.
>
>      We have no good way to determine if the 'reserved memory' mapping
>      is lost. Since all the other threads are not idle, it is possible
>      for another thread to have 'reserved' the same memory space for a
>      different data structure. Our thread could observe that the memory
>      is still 'reserved' but we have no way to know that the reservation
>      isn't ours.
>
> You might be wondering why we can't recover from this transient
> resource availability issue.
>
>      We could retry the failed mmap() commit operation, but we would
>      again run into the issue that we no longer know which data
>      structure 'owns' the 'reserved' memory mapping. In particular, the
>      memory could be reserved by native code calling mmap() directly so
>      the VM really has no way to recover from this failure.