Hi Jini,
Did you see my earlier reply? I might have sent it out during the mail
server outage days :-(
http://openjdk.5641.n7.nabble.com/RFR-S-JDK-8200613-SA-jstack-throws-UnmappedAddressException-with-a-CDS-core-file-td352681.html#a353026
Here was my reply again:
Hi Jini,
The changes looks good to me.
Have you tested this on MacOS? CDS heap support is also enabled on
MacOS. See macros.hpp:
#if INCLUDE_CDS && INCLUDE_G1GC && defined(_LP64) &&
!defined(_WINDOWS)
#define INCLUDE_CDS_JAVA_HEAP 1
Also, besides CDS, do we know how often other files will be mmaped with
MAP_PRIVATE? Will users get huge core files because CDS is enabled? In
JDK 12, CDS will be enabled by default (see JDK-8202951), so all users
will be affected by the following line:
if (UseSharedSpaces) {
set_coredump_filter(FILE_BACKED_PVT_BIT);
}
Maybe you can run an big app such as Eclipse, trigger a core dump, and
compare the size of the core file before/after this change?
Thanks
- Ioi
Thanks
- Ioi
On 10/21/18 8:58 PM, Jini George wrote:
Gentle reminder!
Thanks,
- Jini
On 10/9/2018 11:31 AM, Jini George wrote:
Hello!
[Including runtime-dev since the changes are in runtime code]
Requesting reviews for:
Webrev: http://cr.openjdk.java.net/~jgeorge/8200613/webrev.01/
BugID: https://bugs.openjdk.java.net/browse/JDK-8200613
Issue: jhsdb jstack would throw an UnmappedAddressException with a
core file generated from a CDS enabled java process. This is seen
only with Linux and with G1GC, while trying to read in data from the
shared strings region (the closed archive heap space). This region
(which is a file backed private memory region) is not dumped into the
corefile for Linux. This, being a heap region (and therefore being a
read-write region) is also not read in from the classes.jsa file in
SA since only the read only regions are read in while processing the
core file. (The expectation being that the read write regions are in
the core file).
Proposed solution: The proposed solution is to have the
coredump_filter value corresponding to the CDS process to include bit
2 (file-backed private memory), so that the file-backed private
memory region also gets dumped into the corefile. The proposed fix is
in src/hotspot/os/linux/os_linux.cpp.
Thanks,
Jini.
