On 24/04/08 02:17PM, Patrick Steinhardt wrote: > When seeking a reftable record in a block we need to position the > iterator _before_ the sought-after record so that the next call to > `block_iter_next()` would yield that record. To achieve this, the loop > that performs the linear needs to restore the previous position once it Did we mean to say "linear seek" here? Otherwise this looks good to me. -Justin > has found the record. > > This is done by advancing two `block_iter`s: one to check whether the > next record is our sought-after record, and one that we update after > every iteration. This of course involves quite a lot of copying and also > leads to needless memory allocations. > > Refactor the code to get rid of the `next` iterator and the copying this > involves. Instead, we can restore the previous offset such that the call > to `next` will return the correct record. > > Next to being simpler conceptually this also leads to a nice speedup. > The following benchmark parser 10k refs out of 100k existing refs via > `git-rev-list --no-walk`: > > Benchmark 1: rev-list: print many refs (HEAD~) > Time (mean ± σ): 170.2 ms ± 1.7 ms [User: 86.1 ms, System: 83.6 ms] > Range (min … max): 166.4 ms … 180.3 ms 500 runs > > Benchmark 2: rev-list: print many refs (HEAD~) > Time (mean ± σ): 161.6 ms ± 1.6 ms [User: 78.1 ms, System: 83.0 ms] > Range (min … max): 158.4 ms … 172.3 ms 500 runs > > Summary > rev-list: print many refs (HEAD) ran > 1.05 ± 0.01 times faster than rev-list: print many refs (HEAD~) > > Signed-off-by: Patrick Steinhardt <ps@xxxxxx> ...
