Re: [PATCH 0/5] Suggested for PU: revision caching system to significantly speed up packing/walking

Shawn O. Pearce wrote:

A Large Angry SCM [off-list ref] wrote:

quoted

Shawn O. Pearce wrote:

quoted

Nick Edelen [off-list ref] wrote:

quoted

Hrmm, I just realized that it dosn't actually cache paths/names...

You may not need the path name, but instead the hash value that
pack-objects computes from the path name.

Please do NOT expose the hash values. The hash used by pack-objects is  
an implementation detail of the heuristics used by the _current_ object  
packing code. It would be a real shame to have to maintain backward  
compatibility with it at some future date after the packing machinery  
has changed.

This is a local cache.  If there was a version number in the header,
and the hash function changes, we could just bump the version number
and invalidate all of the caches.

No sense in storing (and doing IO of) huge duplicate string values
for something where we really only need 32 bits, and where a
recompute from scratch only costs a minute.

That will work for me if the cache gets a version number and iff the 
pack-objects hash code gets big warning comments about the cache code 
dependency.