RFR: 8146879: Add option for handling existing log files in UL

[Robbin Ehn]

Hi Marcus,

Two small things.

src/share/vm/runtime/os.hpp:
+  static int compare_file_modified_times(const char* file1, const char* 
file2);
Is this so generic that we should have it os.[h,c]pp?
E.g. if we want to compare ctime, etc.. ?

On 03/11/2016 03:21 PM, Marcus Larsson wrote:
> Third time's the charm.
>
> Webrev:
> http://cr.openjdk.java.net/~mlarsson/8146879/webrev.03/
>
> This patch makes log file rotation the default. Default thresholds are 5
> rotated files with a target size of 20MiB. Truncating behavior can be
> achieved by setting filecount to 0 (-Xlog::myfile.log::filecount=0).

src/share/vm/logging/logFileOutput.hpp:
+ static const size_t DefaultRotationFileSize = 2097152; // 20MiB
Missing a 0 here, I prefer to write this as 20*1024*1024

>
> If a log file already exists during log file initialization it will be
> rotated. If any of the target file names (file.0 to file.4 in the
> default case) are available, that filename will be used for the existing
> log. If all names are taken the VM will attempt to overwrite the oldest
> file.
>
> This should prevent unlimited log file creations and avoid accidental
> loss of log files from previous runs. The default thresholds (5 files,
> 20MiB each) is just a suggestion. If you think it should be higher/lower
> let me know.
>
> Tested with included internal VM tests through RBT.

I also functional tested this and it works as intended.
There is an issue regarding removing the current log file.
Discussed in side-channel it will be handled outside this CS since it 
not directly related.

Otherwise looks good!

/Robbin

>
> Thanks,
> Marcus
>
> On 2016-03-01 15:05, Marcus Larsson wrote:
>> Hi,
>>
>> After some offline discussions I'm withdrawing this patch. I will
>> instead investigate if I can achieve similar behavior using log
>> rotation as the default.
>>
>> Thanks,
>> Marcus
>>
>> On 03/01/2016 12:11 PM, Marcus Larsson wrote:
>>> Hi again,
>>>
>>> Taking a different approach to this.
>>>
>>> New webrev:
>>> http://cr.openjdk.java.net/~mlarsson/8146879/webrev.01/
>>>
>>> Existing files will now by default be renamed/archived with a .X
>>> suffix where X is the lowest number such that the resulting file name
>>> is available (jvm.log becomes jvm.log.0). A mode option for
>>> controlling this behavior has been added as well. It can be set to
>>> archive, append, or truncate (i.e. -Xlog::jvm.log::mode=truncate).
>>>
>>> Tested with included jtreg test through JPRT.
>>>
>>> Thanks,
>>> Marcus
>>>
>>> On 01/14/2016 04:00 PM, Marcus Larsson wrote:
>>>> Hi,
>>>>
>>>> Please review the following patch to make sure UL truncates existing
>>>> log files before writing to them. Since files are opened in append
>>>> mode, truncation isn't done automatically, so instead the patch adds
>>>> an attempt to remove the log file before opening it.
>>>>
>>>> Webrev:
>>>> http://cr.openjdk.java.net/~mlarsson/8146879/webrev.00/
>>>>
>>>> Issue:
>>>> https://bugs.openjdk.java.net/browse/JDK-8146879
>>>>
>>>> Testing:
>>>> Included test through JPRT
>>>>
>>>> Thanks,
>>>> Marcus
>>>
>>
>