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From: Evgeny Kotkov <evgeny.kotkov@visualsvn.com>
Date: Wed, 26 Jul 2017 13:18:00 +0300
Message-ID: <CAP_GPNibuoij6VahwgssBRHp0u+4wusv4rzCgfXHhen+iJGxRw@mail.gmail.com>
Subject: Re: svn commit: r1801940 - in /subversion/trunk: ./ notes/
 subversion/include/ subversion/include/private/ subversion/libsvn_delta/
 subversion/libsvn_fs_fs/ subversion/libsvn_subr/ subversion/tests/libsvn_delta/
 subversion/tests/libsvn_subr/
To: Stefan Sperling <stsp@elego.de>
Cc: Subversion Development <dev@subversion.apache.org>, Daniel Shahaf <d.s@daniel.shahaf.name>,
	commits@subversion.apache.org
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archived-at: Wed, 26 Jul 2017 10:18:26 -0000

Stefan Sperling <stsp@elego.de> writes:

> Does mod_dav_svn really need an option for this?
>
> Can't lz4 (svndiff2) be negotiated as a mutual protocol capability of
> client and server? Why won't a simple logic such as the following work:
>
>   If the client announces lz4 compression level 1 support, use it.
>   Else, use zlib.

The current state is that there are no additional options in mod_dav_svn,
and the "SVNCompression" option has just been discussed as an explicit
alternative to what we have now (but it also has a couple of potential
drawbacks, and I don't plan to implement it at this time).

Currently, the negotiation scheme works similarly to what you have described.
If the server has "SVNCompressionLevel 1", and the client supports LZ4, then
it will be used.  Otherwise, in case of older clients, they will be using zlib
compression with the corresponding compression level.

Apart from this, I was willing to propose that we switch to LZ4 compression
by default for both mod_dav_svn and newly created FSFS repositories.  That
is, by making "1" the default value of SVNCompressionLevel directive and
by making "lz4" the default value of the discussed "compression=" knob in
fsfs.conf.

(I will take this to a separate thread once all the necessary things are
in place.)


Regards,
Evgeny Kotkov