[darcs-devel] Improving pull performance

Florian Weimer fw at deneb.enyo.de
Fri Aug 5 07:38:04 PDT 2005


* David Roundy:

> On Fri, Jul 29, 2005 at 04:21:08PM +0200, Florian Weimer wrote:
>> Has anybody thought about improving pull performance?
>> 
>> I think it might be useful to add a cache for the remote
>> _darcs/inventories/* and _darcs/inventory files, and use zsync to make
>> downloads of _darcs/inventory incremental.
>
> Are you thinking about optimizing the "no changes" case?

Rather the "no tags" case, I think.

> I.e. rather than caching to avoid transport, I'd like to avoid
> downloading any data we don't need.  I don't see any reason why we
> should need zsyncish optimizations for fetching the inventory,
> unless perhaps the inventory is very large because there aren't any
> tags.

My benchmark is John Goerzen's fptools repository (created from
fptools/GHC CVS, see <http://darcs.complete.org/fptools/>).

Your suggestion seems to imply that I wouldn't have to download 4
megabyte of inventory data if John tagged his repository regularly.
Is this true?  Below, you mentioned something about push not splitting
the inventory, would this be relevant in this case?

> And as long as the inventory is small, latency will
> dominate, and a simple download should beat zsync in speed.

Sure, but at 4 MB, things are a bit different.




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