This exercise of estimating a good spot to gain performance with parallelism at git seems more difficult than I thought, firstly. Also, I'm not that familiar yet with git packing (neither with the sections of it that could benefit from parallelism). So could anyone point me some good references on this, where I could study and maybe come back with more valuable suggestions? On Tue, Mar 5, 2019 at 9:57 AM Duy Nguyen <pclouds@xxxxxxxxx> wrote: > > On Tue, Mar 5, 2019 at 11:51 AM Jeff King <peff@xxxxxxxx> wrote: > > > processing power from multiple cores, but about _not_ blocking. I > > > think one example use case here is parallel checkout. While one thread > > > is blocked by pack access code for whatever reason, the others can > > > still continue doing other stuff (e.g. write the checked out file to > > > disk) or even access the pack again to check more things out. > > Hmm, you mean distributing the process of inflating, reconstructing deltas and checking out files between the threads? (having each one doing the process for a different file?) > > I'm not sure if it would help much for packs, because they're organized > > to have pretty good cold-cache read-ahead behavior. But who knows until > > we measure it. > > > > I do suspect that inflating (and delta reconstruction) done in parallel > > could be a win for git-grep, especially if you have a really simple > > regex that is quick to search. > > Maybe git-blame too. But this is based purely on me watching CPU > utilization of one command with hot cache. For git-blame though, diff > code as to be thread safe too but that's another story. I don't know if this relates to parallelizing pack access, but I thought that sharing this with you all could perhaps bring some new insights (maybe even on parallelizing some other git section): I asked my friends who contribute to the Linux Kernel what git commands seems to take longer during their kernel work, and the answers were: - git log and git status, sometimes - using pager's search at git log - checking out to an old commit - git log --oneline --decorate --graph
