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From: "Bert Huijben" <bert@qqmail.nl>
To: "'Ivan Zhakov'" <ivan@visualsvn.com>
Cc: <dev@subversion.apache.org>
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Subject: RE: svn commit: r1716575 - in
 /subversion/trunk/subversion/libsvn_ra_serf: commit.c ra_serf.h util.c
Date: Thu, 26 Nov 2015 10:11:08 +0100
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> -----Original Message-----
> From: Ivan Zhakov [mailto:ivan@visualsvn.com]
> Sent: donderdag 26 november 2015 09:54
> To: Bert Huijben <bert@qqmail.nl>
> Cc: dev@subversion.apache.org
> Subject: Re: svn commit: r1716575 - in
> /subversion/trunk/subversion/libsvn_ra_serf: commit.c ra_serf.h util.c
>=20
> On 26 November 2015 at 11:41, Bert Huijben <bert@qqmail.nl> wrote:
> >> -----Original Message-----
> >> From: Ivan Zhakov [mailto:ivan@visualsvn.com]
> >> Sent: donderdag 26 november 2015 09:19
> >> To: dev@subversion.apache.org; Bert Huijben <bert@qqmail.nl>
> >> Subject: Re: svn commit: r1716575 - in
> >> /subversion/trunk/subversion/libsvn_ra_serf: commit.c ra_serf.h =
util.c
> >>
> >> On 26 November 2015 at 11:05, <rhuijben@apache.org> wrote:
> >> >
> >> > Author: rhuijben
> >> > Date: Thu Nov 26 08:05:36 2015
> >> > New Revision: 1716575
> >> >
> >> > URL: http://svn.apache.org/viewvc?rev=3D1716575&view=3Drev
> >> > Log:
> >> > In ra_serf: when a to-be committed file has text and property =
changes
> to
> >> be
> >> > applied, pipeline both requests.
> >> >
> >> This could fail over HTTP/2 if both pipelined requests will be =
handled
> >> by different worker threads: FSFS doesn't allow concurrent access =
to
> >> transactions.
> >
> > I'm surprised to learn that. I would have guessed concurrent access =
was
> > always part of the design of the fs layer, by the way we use it in =
mod_dav.
> >
> > I hope we can somehow lift that restriction, as improving commit
> performance
> > over mod_dav is high on a few wish lists.
> >
> First of all I'm not sure that concurrent *writing* could speed up
> commit: there is no fsync() calls when working with transactions. As
> far I remember svn:// also waits for every TXN operation to complete
> before sending next one, so svn:// and http:// performance should be
> the same when working over high-latency network.

No, in svn:// the client sends out all the requests and only peeks the =
connection to see if there is waiting data (an error) during commit. The =
client only waits for the server after the entire commit is completed. =
Not after every txn operation.

This is why 'in general' you get not identical error reporting on =
commits when you use svn:// (or svn+ssh://, etc.). In many cases the =
only failure you see is the text from the server as the client doesn't =
even know which file/directory failed during the commit.

With a bit of luck you receive errors a bit earlier than the final =
commit step. But with <=3D 1.9.0 this didn't work for svn+ssh:// on =
Windows at all. (We handled the error for not implemented as if no data =
was waiting)

	Bert