[PATCH 5 of 6 V2] obscache: instantiate the cache and keep it warm

[Jun Wu]

Excerpts from Pierre-Yves David's message of 2017-05-23 20:20:49 +0200:
> 
> On 05/23/2017 05:07 PM, Jun Wu wrote:
> > Excerpts from Pierre-Yves David's message of 2017-05-23 11:49:49 +0200:
> >> [...]
> >> Does these details address your concerns?
> >
> > There are some automation which does reclones. Reclone could be done in
> > seconds. 9 seconds obscache build time does look a bit painful for them.
> 
> Out of curiosity, what order of magnitude of "seconds" are we talking 
> about here? What kind of extra setup do you use (beside remotefilelog) 
> to achieves that kind of timing for such large repository ?

The initial stream clone takes 13 seconds to download full changelog and
manifest. Update is slow but a user-space filesystem will remove that cost.
In the near future, we may migrate to some kind of lazy manifest so stream
clone can skip manifest revlog and the time could be cut in half.

> > So I'd like to see a config option to opt out the cache.
> 
> I can certainly adds that.
> 
> Cheers
>