Hi,
I've observed a poor performances issue when using glob(starstar/whatever).
I know this is a known issue, I just had to look at the first lines of
unix_expandpath().
And yet, we could do better. Much better.
I've run a simple test case in callgrind:
> valgrind --tool=callgrind ./vim -U NONE -u NONE -c "echo
> glob('~/.vim/**/tags')" -c q
On my current machine, I see vim_regexec() and vim_regcomp() executed 14036
times, and taking respectively 41.72% + 15.67% of unix_expandpath() (lr) cycles
measured by callgrind.
Investigating further, I've seen that simply by caching `regmatch.regprog` when
`starstar` is true and `e-s==2`, vim_regcomp() is executed now only **once** on
my test case. From 363879003 cycles in unix_expandpath() I do down to
291294681. This looks like a good start.
static regprog_T *reg_starstar = NULL;
if (!reg_starstar) {
reg_starstar = reg_starstar_compute();
}
...
if (starstar && (e-s == 2))
{
onlystarstar = TRUE;
regmatch.regprog = reg_starstar;
if (regmatch.regprog == NULL) {
vim_free(buf);
return 0;
}
} else { old code, rearranged, of course }
And I wonder. Do we really need to apply regmatch when we know we are in a
"starstar" situation? Can't we simply go down to the next sub-directory?
BTW, on another topic, I've also executed
> vim -U NONE -u NONE -c "echo glob('~/.vim/**5/tags')" -c q
which yields no result on v 8.0.502, un-patched, and on my patched v8.0.563
If I understand the documentation correctly, this looks like a bug.
--
Luc Hermitte
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