perf: avoid actual writing branch cache out correctly Mercurial 2.5 (or 9b6ae29d4801) introduced "perfbranchmap" command, and tried to avoid actual writing branch cache out by replacing write() of branchcache class in branchmap.py with no-op function (probably, for elimination of noisy and heavy file I/O factor). But its implementation isn't correct, because 9b6ae29d4801 replaced not branchmap.branchcache.write() but branchmap.write(). The latter doesn't exist, even at that change. To avoid actual writing branch cache out correctly, this patch replaces branchmap.branchcache.write() with no-op function. To detect mistake of replacement or change of API in the future quickly, this patch uses safeattrsetter() instead of direct attribute assignment. For similarity between replacements, this patch also changes replacement of branchmap.read(). In this patch, replacement of read()/write() can run safely outside "try" block, because two safeattrsetter() invocations ensure that replacement doesn't cause exception. FYI, the table below compares "base" filter wall time of perfbranchmap on recent mozilla-central repo with each Mercurial version between before and after this patch. ==== ========= ========= ver before after ==== ========= ========= 2.5 18.492334 18.232455 2.6 18.733858 18.156702 2.7 18.245598 18.349210 2.8 18.289070 18.528422 2.9 17.572742 16.989655 3.0 17.406953 17.615012 3.1 17.228419 17.689805 3.2 17.862961 17.718367 3.3 2.632110 2.707960 3.4 3.285683 3.272060 3.5 3.370141 3.352176 3.6 3.366939 3.242455 3.7 3.300778 3.367328 3.8 3.300132 3.267298 3.9 3.418996 3.370265 ==== ========= ========= IMHO, there is no serious overlooking performance regression.

perf: get subsettable from appropriate module for Mercurial earlier than 2.9 Before this patch, using branchmap.subsettable prevents perfbranchmap from measuring performance of Mercurial earlier than 2.9 (or 175c6fd8cacc), because 175c6fd8cacc moved subsettable from repoview.py to branchmap.py, even though there are some code paths for Mercurial earlier than 2.9 in perf.py. For example, setting "_prereadsize" attribute in perfindex() and perfnodelookup() is effective only with hg earlier than 1.8 (or 61c9bc3da402). To get subsettable from appropriate module, this patch examines existence of subsettable in branchmap and repoview. This patch also adds check-perf-code.py an extra check entry to detect direct usage of subsettable attribute in perf.py.

perf: introduce safeattrsetter to replace direct attribute assignment Referring not-existing attribute immediately causes failure, but assigning a value to such attribute doesn't. For example, perf.py has code paths below, which assign a value to not-existing attribute. This causes incorrect performance measurement, but these code paths are executed successfully. - "repo._tags = None" in perftags() recent Mercurial has tags cache information in repo._tagscache - "branchmap.write = lambda repo: None" in perfbranchmap() branchmap cache is written out by branchcache.write() in branchmap.py "util.safehasattr() before assignment" can avoid this issue, but might increase mistake at "copy & paste" attribute name or so. To centralize (1) examining existence of, (2) assigning a value to, and (3) restoring an old value to the attribute, this patch introduces safeattrsetter(). This is used to replace direct attribute assignment in subsequent patches. Encapsulation of restoring is needed to completely remove direct attribute assignment from perf.py, even though restoring isn't needed so often.

largefiles: use context for file closing Make the code slightly smaller and safer (and more deeply indented).

largefiles: when setting/clearing x bit on largefiles, don't change other bits It is only the X bit that it matters to copy from the standin to the largefile in the working directory. While it generally doesn't do any harm to copy the whole mode, it is also "wrong" to copy more than the X bit we care about. It can make a difference if someone should try to handle largefiles differently, such as marking them read-only. Thus, do similar to what utils.setflags does and set the X bit where there are R bits and obey umask.

eol: on update, only re-check files if filtering changed Before, update would mark all files as 'normallookup' in dirstate if .hgeol changed so all files would get the new filtering applied. That takes some time ... and is pointless if the filtering for that file didn't change. Instead, keep track of the old filtering and only check files where the filtering is changed. To keep the old filtering, change to write the applied .hgeol content to .hg/eol.cache instead of just touching it. That change is backwards/forwards compatible. In a real world test, this takes an update that is changing .hgeol and 30000 files from 12s to 4s - where the remaining eol overhead is 1-2s.

dirs: add comment about _PyBytes_Resize So readers have a canonical function to compare this code to.

checkcopies: extract the '_related' closure There is not need for it to be a closure.

checkcopies: add an inline comment about the '_related' call This helps understanding the flow of the function.

checkcopies: minor change to comment This helped me understand the refactoring so this must be helpful.

checkcopies: rename 'ca' to 'base' This variable was named after the common ancestor. It is actually the merge base that might differ from the common ancestor in the graft case. We rename the variable before a larger refactoring to clarify the situation.

bisect: extra a small initialisation outside of a loop Having initialisation done during the first iteration is cute, but can be avoided.