On Thu, Jun 11, 2009 at 12:44 PM, Dan Pascu<[email protected]> wrote:
>
> On 11 Jun 2009, at 11:19, Petr Rockai wrote:
>
>> Nathan Gray <[email protected]> writes:
>>>
>>> On Wed, Jun 10, 2009 at 09:55:32AM +0200, Petr Rockai wrote:
>>>>
>>>> Moreover, I should start looking into getting us a new pristine format
>>>> that I
>>>> have promised in my application (the indexed working directory is,
>>>> obviously,
>>>> just a part of the whole deal).
>>>
>>> If I remember correctly, this has to do with setting up a subdirectory
>>> structure for the files in the pristine cache, so the files are not
>>> all in a single directory.
>>
>> Partially. It is also about packing up the many small files into bigger
>> chunks,
>> so http transfers are more efficient (ie. fewer roundtrips and less
>> overhead).
>
> Wouldn't a persistent http connection serve better this purpose? Starting
> with version 1.1 the http protocol supports keep-alive, which means you only
> have to make 1 connection and can fetch all the files over it. I believe
> that making a lot of one shot connections that only fetch one file is much
> more taxing than the fact that there are many files to transfer. I think
> that making less connections can result in a better improvement than
> reducing the number of files to fetch, unless that number becomes 1. This is
> more apparent in the case of https where the initial connection setup is
> very expensive.
>
> In the end both techniques could be applied, it's just my belief that using
> keep-alive can provide a larger improvement, with less effort. Later we
> could see if grouping small files together provides any significant
> improvement over that or it's just marginal, in which case the extra
> complexity is probably not worth it.

Dacas used persistent connections for a long time. Darcs 2 tries to
use pipelining. But still each request/response add significant
overhead.

I believe it would really pay off if we reduce the number of files
needed to be downloaded (several thousands for darcs darcs repo).

Regards,
  Dmitry

>
> --
> Dan
>
>
>
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