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Re: svn commit: r1637184 - in /subversion/trunk/subversion: libsvn_fs_fs/ tests/libsvn_fs/

From: Ivan Zhakov <ivan_at_visualsvn.com>
Date: Fri, 7 Nov 2014 18:17:38 +0300

On 7 November 2014 02:44, Stefan Fuhrmann <stefan.fuhrmann_at_wandisco.com> wrote:
> [This goes mostly to Ivan but the last part goes to Brane. Don't want to
> sub-thread here.]
>
> On Thu, Nov 6, 2014 at 8:24 PM, Branko Čibej <brane_at_wandisco.com> wrote:
>>
>> On 06.11.2014 20:03, ivan_at_apache.org wrote:
>> > Author: ivan
>> > Date: Thu Nov 6 19:03:31 2014
>> > New Revision: 1637184
>> >
>> > URL: http://svn.apache.org/r1637184
>> > Log:
>> > Make FSFSv7 repositories always use consistent addressing mode, instead
>> > of
>> > saving revision number from which logical addressing was enabled.
>>
>>
>> Congrats on finally doing something concrete about FSFSv7.
>
>
> +1 on the meta point.
>
> It looks a bit like a rushed commit, though (partly corrected by the
> r1637186 commit). Documentation update is missing:
>
> structure:Filesystem format options
> * update addressing mode description
>
> fs_fs.c:read_format()
> * update docstring
>
> transaction.c:store_l2p_index_entry()
> * update docstring
>
Thanks for review! I've fixed these typos in r1637330.

> I'm -.5 on removing the "mixed addressing" feature for exactly the
> points made by Brane.

I'm going to reply on your comments a bit later.

> Brane, you might confuse this with 'svnadmin pack'. The thing
> about upgrade is that we have a nasty FS API limitation that
> is a missing concept of read sessions / locks.

But I want to comment this one particular and important thing right
now. Please do not treat all things that are unclear for you as
a "nasty limitations".

Missing of read sessions/locks is a core (and pretty successful)
design decision of the FSFS. Quoting original Greg Hudson email
in 2004 [1]:
[[[
* Despite the above, scalability may be better, because there are no
  read-locks and no potential interference between readers and other
  readers, or between readers and writers.
]]]

This solution is perfectly works for ten (!) years. If you want to change
(or beat) this approach, please do this in the experimental FSX
format. All other 'revolutionary' FSFS-related performance improvements
should be also implemented there.

[1] http://svn.haxx.se/dev/archive-2004-05/1104.shtml

-- 
Ivan Zhakov
Received on 2014-11-07 16:18:29 CET

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