RFR: 8267155: runtime/os/TestTracePageSizes times out [v5]

[Thomas Stuefe]

> This Linux-specific test parses `/proc/self/smaps` using a dotall regular expression. If part of the expression don't match it explodes in complexity, leading to timeouts.
> 
> In our case, `VmFlags` tag was missing from smaps, which was introduced with kernel 3.8. I am actually not able to determine how slow they were; on one machine they ran for two hours before getting killed.
> 
> I tried to fiddle with the regular expression and gave up, instead opting to rewrite the parser to get a simple one-pass scan. This is way faster than before - on our old-kernel machines the tests complete in 2 minutes. On new kernels the test is a bit faster too.
> 
> In addition to rewriting the parser, I added code which copies the smaps file into the test directory before parsing it. I do this to minimize problems should the underlying proc fs content change while parsing, and to have a way to retain the parsed smaps files.
> 
> I also added a way to feed an external smaps file into the test. Of course the test would fail, but it was a way to test the parser.
> 
> Unfortunately, this does not make the test succeed. The timeouts are gone, but we have still have no way to know if TPHs are enabled or not. That is a separate issue though.
> 
> Thanks, Thomas

Thomas Stuefe has updated the pull request incrementally with four additional commits since the last revision:

 - fixes
 - made kernel 3.8 mandatory
 - Merge branch 'JDK-8267155-runtime-os-TestTracePageSize-times-out' of github.com:tstuefe/jdk into JDK-8267155-runtime-os-TestTracePageSize-times-out
 - wip

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4064/files
  - new: https://git.openjdk.java.net/jdk/pull/4064/files/d5785cbf..0e2a9e31

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4064&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4064&range=03-04

  Stats: 59 lines in 1 file changed: 42 ins; 7 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4064.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4064/head:pull/4064

PR: https://git.openjdk.java.net/jdk/pull/4064