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Re: possible optimization on update at externals with fixed-revision number?

From: Johan Corveleyn <jcorvel_at_gmail.com>
Date: Fri, 24 Jan 2014 14:28:45 +0100

On Fri, Jan 24, 2014 at 2:22 PM, Branko Čibej <brane_at_wandisco.com> wrote:
> On 24.01.2014 14:09, Stefan Sperling wrote:
>
> On Thu, Jan 23, 2014 at 01:11:36PM +0000, Kuno Meyer wrote:
>
> Hi all,
>
> One of the repositories I am working with has a long list of "svn:external"
> links. This has a major impact on working copy update performance, since
> each external link needs an additional roundtrip to the (painfully slow) SVN
> server. So it can easily be the case that the update of the main working
> copy (several 10k files) is done in <10 seconds, but querying the 40-45
> external repository takes another 60-80 seconds.
>
> However, since the external links are all fixed to a specific revision
> number, and since the working copy knows its current reference revision
> number, why do you have to roundtrip to the SVN server anyway? Wouldn't it
> be safe to omit the server roundtrip, under the assumption that a published
> revision is immutable?
>
> Yes in principle, but the external working copy must have been tampered
> with. E.g. it must not contain mixed revisions.
>
> And non-pinned externals inside of pinned externals need to be handled
> properly.
>
> There may be more restrictions I'm not aware of right now.
> Many retrictions can be determined cheaply by querying the external
> working copy's database, but some may need a disk crawl.
>
> At least in my case, this would result in a speedup of "svn update" of
> factor 5-15 in the case of no or only a only few changesets to download.
>
> Please file an ENHANCEMENT issue for this. I like the idea.
>
>
> I think we'd get much better performance if we parallelized externals
> handling. I'm not aware of any reason (apart from serializing notifications)
> why this wouldn't work, as long as the externals have separate working
> copies.

That would be a more general improvement, making all externals updates
faster (not only the pinned ones). However, "doing no work" should
still be faster than "doing N things in parallel" :-), so that would
be an additional saving for externals I guess.

-- 
Johan
Received on 2014-01-24 14:29:40 CET

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