Re: [PATCH v2 0/4] Speed up unpack_trees()

[Ben Peart <peartben@gmail.com>]

On 7/29/2018 6:33 AM, Nguyễn Thái Ngọc Duy wrote:
> This series speeds up unpack_trees() a bit by using cache-tree.
> unpack-trees could bit split in three big parts
> 
> - the actual tree unpacking and running n-way merging
> - update worktree, which could be expensive depending on how much I/O
>    is involved
> - repair cache-tree
> 
> This series focuses on the first part alone and could give 700%
> speedup (best case possible scenario, real life ones probably not that
> impressive).
> 
> It also shows that the reparing cache-tree is kinda expensive. I have
> an idea of reusing cache-tree from the original index, but I'll leave
> that to Ben or others to try out and see if it helps at all.
> 
> v2 fixes the comments from Junio, adds more performance tracing and
> reduces the cost of adding index entries.
> 
> Nguyễn Thái Ngọc Duy (4):
>    unpack-trees.c: add performance tracing
>    unpack-trees: optimize walking same trees with cache-tree
>    unpack-trees: reduce malloc in cache-tree walk
>    unpack-trees: cheaper index update when walking by cache-tree
> 
>   cache-tree.c   |   2 +
>   cache.h        |   1 +
>   read-cache.c   |   3 +-
>   unpack-trees.c | 161 ++++++++++++++++++++++++++++++++++++++++++++++++-
>   unpack-trees.h |   1 +
>   5 files changed, 166 insertions(+), 2 deletions(-)
> 

I have a limited understanding of this code path so I'm not the best 
person to review this but I didn't see any issues that concerned me.  I 
also was able to run our internal functional and performance tests in 
addition to the git tests and the results were positive.

Ben