On Tue, 20 Aug 2024 06:13:18 GMT, Stefan Karlsson <stef...@openjdk.org> wrote:
>> So in this test case: >> `-Xlog:gc,gc+init` >> you have it so that `true` is returned. >> >> With this line of code: >> ``` >> const bool is_gc_exact_match = ts->contains(LogTag::_gc) && ts->ntags() >> == 1; >> >> I would think that this part is `false`: `ts->ntags() == 1` >> for the `-Xlog:gc,gc+init` test case so we'll be returning `false`. >> >> What am I missing? > > The important part is that `ts` contains one single tag set and that > `gc,gc+init` is a string that specifies the two tag sets `gc` and `gc+init`. > Also, note that `-Xlog:gc,gc+init` and `-Xlog:gc -Xlog:gc+init` is > effectively the same. > > It is also important to understand that the for loop iterates over all tag > sets that have been used in the HotSpot code. It is not iterating over the > tag sets specified by -Xlog lines. OK, I get it now. The loop cycles thru the tag set and finds one that is a singleton and an exact match, i.e., `-Xlog:gc`. With `-Xlog:gc+init`, the `ts->ntags() == 1` would be `false` because that one is not an exact match. I misunderstood the algorithm a bit. Sorry for the noise. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20628#discussion_r1723555244
