On 2/23/16 5:56 AM, Thomas Stüfe wrote:
Hi Cheleswer,
On Tue, Feb 23, 2016 at 9:38 AM, Cheleswer Sahu <cheleswer.s...@oracle.com>
wrote:
Hi,
Please review the code changes for
https://bugs.openjdk.java.net/browse/JDK-8146683 .
Webrev link: http://cr.openjdk.java.net/~csahu/8146683/
JBS Link: https://bugs.openjdk.java.net/browse/JDK-8146683
Bug Brief:
While investigating bug https://bugs.openjdk.java.net/browse/JDK-8144483
it has been observed that "check_addr0() " function is not written
efficiently.
This function is trying to read each "prmap_t" entry in "/proc/self/map"
file one by one which is time taking and can cause in long pauses.
Solution proposed:
Instead of reading each "prmap_t" entry in "/proc/self/map" file one by
one, read the entries in chunks. There can be many entries in "map" file,
so I have decided to read these
in chunks of 100 "prmap_t" entries. Reading entries in chunks saves a lot
of read calls and results in smaller pause times.
Regards,
Cheleswer
We saw cases, especially on Solaris, where the content of a file in the
proc file system changed under us while we were reading it. So this should
be kept in mind. The original code seems also broken in that regard,
because it assumes the ::read() call to read the full size of a prmap_t
entry, but it may theoretically read an incomplete entry.
As for your coding, you first estimate the size of the mapping file and
then use this to determine how many entries to read; but when reading, this
information may already be stale. I think it would be more robust and also
simpler to just try to read as many entries as possible - in chunks, to
make reading faster - until you get EOF.
Kind Regards, Thomas
I'm really sure that we've been down this road before. In particular,
Dmitry Samersoff has worked on this issue (or one very much like it)
before, but he is on vacation until the end of the month.
Dan
On Tue, Feb 23, 2016 at 9:38 AM, Cheleswer Sahu <cheleswer.s...@oracle.com>
wrote:
Hi,
Please review the code changes for
https://bugs.openjdk.java.net/browse/JDK-8146683 .
Webrev link: http://cr.openjdk.java.net/~csahu/8146683/
JBS Link: https://bugs.openjdk.java.net/browse/JDK-8146683
Bug Brief:
While investigating bug https://bugs.openjdk.java.net/browse/JDK-8144483
it has been observed that "check_addr0() " function is not written
efficiently.
This function is trying to read each "prmap_t" entry in "/proc/self/map"
file one by one which is time taking and can cause in long pauses.
Solution proposed:
Instead of reading each "prmap_t" entry in "/proc/self/map" file one by
one, read the entries in chunks. There can be many entries in "map" file,
so I have decided to read these
in chunks of 100 "prmap_t" entries. Reading entries in chunks saves a lot
of read calls and results in smaller pause times.
Regards,
Cheleswer
