parsers: inline fields of dirstate values in C version Previously, while unpacking the dirstate we'd create 3-4 new CPython objects for most dirstate values: - the state is a single character string, which is pooled by CPython - the mode is a new object if it isn't 0 due to being in the lookup set - the size is a new object if it is greater than 255 - the mtime is a new object if it isn't -1 due to being in the lookup set - the tuple to contain them all In some cases such as regular hg status, we actually look at all the objects. In other cases like hg add, hg status for a subdirectory, or hg status with the third-party hgwatchman enabled, we look at almost none of the objects. This patch eliminates most object creation in these cases by defining a custom C struct that is exposed to Python with an interface similar to a tuple. Only when tuple elements are actually requested are the respective objects created. The gains, where they're expected, are significant. The following tests are run against a working copy with over 270,000 files. parse_dirstate becomes significantly faster: $ hg perfdirstate before: wall 0.186437 comb 0.180000 user 0.160000 sys 0.020000 (best of 35) after: wall 0.093158 comb 0.100000 user 0.090000 sys 0.010000 (best of 95) and as a result, several commands benefit: $ time hg status # with hgwatchman enabled before: 0.42s user 0.14s system 99% cpu 0.563 total after: 0.34s user 0.12s system 99% cpu 0.471 total $ time hg add new-file before: 0.85s user 0.18s system 99% cpu 1.033 total after: 0.76s user 0.17s system 99% cpu 0.931 total There is a slight regression in regular status performance, but this is fixed in an upcoming patch.