Re: [Patch] Losing many samples when profiling multiple JVMs
William Cohen <[email protected]>
| Newsgroups | gmane.linux.oprofile |
|---|---|
| Message-ID | <[email protected]> |
On 06/12/2015 04:49 PM, 大平怜 wrote: > Hi, > > Anyone has any suggestions? I hope my patch is included in OProfile-1.1. > > > Thanks, > Rei Odaira > > 2015-05-31 22:00 GMT-05:00 大平怜 <[email protected] <mailto:[email protected]>>: > > Hi, > > I found when profiling multiple JVMs, many samples that should have hit JITted methods were lost due to no permanent mapping. This was because OProfile did not have correct operf_mmap for the JITted code anon regions of some of the JVMs. This error can happen as follows: > > (1) __handle_mmap_event() creates a new operf_mmap for a small anon region of a JVM. > (2) When another JVM happens to allocate its anon region at the same starting virtual address but with a larger size, __handle_mmap_event() first searches all_images_map. > (3) __handle_mmap_event() finds the previously created operf_mmap in all_images_map and reuses it, because it checks only filename and start_addr. > (4) As a result, when a sample hits a JITted method that was generated between the incorrect end_addr and the actual end address, __get_operf_trans() cannot find an appropriate mapping. > > The root cause of this problem is that __handle_mmap_event() does not check end_addr when searching all_images_map. This should work for a normal file, which should have the same size when mapped to different processes, but not for anon regions, which can have different sizes in different processes. The attached patch will add this check. > > More fundamentally, I am wondering what the purpose of all_images_region is. I guess it is to reuse operf_mmap structures for more than one processes. The file names in all_images_map are stored in absolute paths, but they are compared against a file base name in __handle_mmap_event(). As a result, this comparison succeeds only for anon and [vdso]. Is this intended behavior? > > > Regards, > Rei Odaira > Hi Rei, Sorry, I missed that earlier patch email. I will take a look at it today. Thanks for testing out the oprofile jvm support and analyzing the issues. -Will ------------------------------------------------------------------------------ _______________________________________________ oprofile-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/oprofile-list