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

[David Holmes]

Perfect!

Thanks Dan.

David
-----

On 28/05/2013 12:43 AM, Daniel D. Daugherty wrote:
> Thanks for the rereview!
>
>
> On 5/26/13 10:50 PM, David Holmes wrote:
>> 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.
>
> Had to reread this a couple of times. My brain kept getting stuck on
> the fact that I didn't use strerror... Once I realized that you meant:
>
>     you can also use strerror to output more meaningful text about the
> error.
>
> it made more sense. Not enough coffee yet... Yes, I can use strerror()
> and that would better. I don't normally use strerror() because I prefer
> numeric values. Old habits die hard...
>
> How about something like this:
>
> $ diff src/os/bsd/vm/os_bsd.cpp{.cr1,}
> 2002c2002,2003
> <           ", %d) failed; errno=%d", addr, size, exec, err);
> ---
>  >           ", %d) failed; error='%s' (errno=%d)", addr, size, exec,
>  >           strerror(err), err);
>
> $ diff src/os/linux/vm/os_linux.cpp{.cr1,}
> 2574c2574,2575
> <             ", %d) failed; errno=%d", addr, size, exec, err);
> ---
>  >             ", %d) failed; error='%s' (errno=%d)", addr, size, exec,
>  >             strerror(err), err);
> 2616,2617c2617,2618
> <               ", " SIZE_FORMAT ", %d) failed; errno=%d", addr, size,
> <               alignment_hint, exec, err);
> ---
>  >               ", " SIZE_FORMAT ", %d) failed; error='%s' (errno=%d)",
> addr,
>  >               size, alignment_hint, exec, strerror(err), err);
>
> $ diff src/os/solaris/vm/os_solaris.cpp{.cr1,}
> 2754c2754,2755
> <             ", %d) failed; errno=%d", addr, bytes, exec, errno);
> ---
>  >             ", %d) failed; error='%s' (errno=%d)", addr, bytes, exec,
>  >             strerror(err), err);
>
>
> so we get the 'meaningful text' and the errno (in parens)...
>
> Dan
>
>
>
>>
>> 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.
>