D1568: lfs: using workers in lfs prefetch

[wlis (Wojciech Lis)]

wlis added a comment.


  @mharbison72 I am not sure if these tests are able to satisfy conditions to actually multithread. But you are right it there is an issue we can force 1 worker.
  The workers on posix are implemented by forking and the only way of communication is through pipes created by worker.py code. Once forked they only communicate every some # of tasks (file fetches in this case) has been finished by the worker (I think # ~ 100 but not sure). We would have to change POSIX behaviour to allow reporting smaller pieces of progress through pipe (potentially 0 tasks finished). This would need changes in bunch of layers (worker, merge, blobstore) instead the current simple use of progress(...) function.
  It is possible to implement that communication, but it is significant amount of work and testing.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D1568

To: wlis, #hg-reviewers, quark, mharbison72
Cc: mharbison72, quark, mercurial-devel