Vicent Marti <tanoku@xxxxxxxxx> writes:
> Calling `git rev-list --use-bitmaps [committish]` is the equivalent
> of `git rev-list --objects`, but the rev list is performed based on
> a bitmap result instead of using a manual counting objects phase.
Why would we ever want to not --use-bitmaps, once it actually works?
I.e., shouldn't this be the default if pack.usebitmaps is set (or
possibly even core.usebitmaps for these things)?
> These are some example timings for `torvalds/linux`:
>
> $ time ../git/git rev-list --objects master > /dev/null
>
> real 0m25.567s
> user 0m25.148s
> sys 0m0.384s
>
> $ time ../git/git rev-list --use-bitmaps master > /dev/null
>
> real 0m0.393s
> user 0m0.356s
> sys 0m0.036s
I see your badass numbers, and raise you a critical issue:
$ time git rev-list --use-bitmaps --count --left-right origin/pu...origin/next
Segmentation fault
real 0m0.408s
user 0m0.383s
sys 0m0.022s
It actually seems to be related solely to having negated commits in the
walk:
thomas@linux-k42r:~/g(next u+65)$ time git rev-list --use-bitmaps --count origin/pu
32315
real 0m0.041s
user 0m0.034s
sys 0m0.006s
thomas@linux-k42r:~/g(next u+65)$ time git rev-list --use-bitmaps --count origin/pu ^origin/next
Segmentation fault
real 0m0.460s
user 0m0.214s
sys 0m0.244s
I also can't help noticing that the time spent generating the segfault
would have sufficed to generate the answer "the old way" as well:
$ time git rev-list --count --left-right origin/pu...origin/next
189 125
real 0m0.409s
user 0m0.386s
sys 0m0.022s
Can we use the same trick to speed up merge base computation and then
--left-right? The latter is a component of __git_ps1 and can get
somewhat slow in some cases, so it would be nice to make it really fast,
too.
--
Thomas Rast
trast@{inf,student}.ethz.ch
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