We noticed an instance where writing multi-pack-index bitmaps was taking a
lot of memory. This small change can reduce the memory pressure slightly
(~25%), but more will be needed to significantly reduce the memory pressure.
Such a change would require updating the bitmap writing code to use on-disk
data structures instead. This is particularly tricky when the
multi-pack-index has not been fully written, because we don't want a point
in time where the object store has a new multi-pack-index without a
reachability bitmap.

Updates in v2
=============

To reduce confusion on the lifetime of 'ctx.entries', some refactoring
patches are inserted to first extract the use of 'ctx' out of
write_midx_bitmap() and into write_midx_internal(). This makes the
FREE_AND_NULL() stand out more clearly.

Thanks, -Stolee

Derrick Stolee (3):
  pack-bitmap-write: use const for hashes
  midx: extract bitmap write setup
  midx: reduce memory pressure while writing bitmaps

 midx.c              | 69 +++++++++++++++++++++++++++++----------------
 pack-bitmap-write.c |  2 +-
 pack-bitmap.h       |  2 +-
 3 files changed, 47 insertions(+), 26 deletions(-)

base-commit: 9dd64cb4d310986dd7b8ca7fff92f9b61e0bd21a

Submitted-As: https://lore.kernel.org/git/pull.1292.v2.git.1658244366.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1292.git.1658176565751.gitgitgadget@gmail.com