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Re: Slow ISVNClient.getChangelists on Linux/NFS share

From: Thomas Singer <thomas.singer_at_syntevo.com>
Date: Thu, 19 Oct 2017 10:07:56 +0200

On 2017-10-19 9:05, Branko Čibej wrote:
> On 19.10.2017 08:30, Thomas Singer wrote:
>> On 18.10.2017 19:56, Branko Čibej wrote:
>>> On 18.10.2017 13:31, Thomas Singer wrote:
>>>> Hi,
>>>>
>>>> When performing following steps on my old Linux test machine (with
>>>> slow hard disk):
>>>>
>>>> - have a SVN working copy at /home/user/test
>>>> - sudo apt install nfs-kernel-server
>>>> - add following line to /etc/exports:
>>>>    /home/user/test *(rw,sync,no_root_squash)
>>>> - start the NFS server:
>>>>    sudo systemctl start nfs-kernel-server.service
>>>> - mount the NFS share:
>>>>    sudo mount localhost:/home/user/test /home/user/test.nfs
>>>>
>>>> and then open /home/user/test.nfs in SmartSVN 9.2 (using SVN 1.9
>>>> JavaHL binaries), adding/removing a file is very slow. It boils down
>>>> to the call ISVNClient.getChangelists which takes ~8s on the NFS share
>>>> (/home/user/test.nfs). First, I thought, it would be caused by the
>>>> native-Java overhead calling the call-back ~11,000 times for my
>>>> working copy, but when using the working copy directly
>>>> (/home/user/test), the method just takes <1s though the ~11,000 times
>>>> call-back invocations are still there.
>>>>
>>>> My working copy has no local modifications, no untracked or ignored
>>>> files, no changelists.
>>>>
>>>> Is it expected that this method (ISVNClient.getChangelists) is so slow
>>>> on a NFS share even if there are no changelists?
>>>
>>> I don't know if it's "expected" but I bet that NFS is killing SQLite
>>> performance.
>>>
>>> https://www.mail-archive.com/sqlite-users@mailinglists.sqlite.org/msg88989.html
>>>
>>>
>>> I'm not sure about the reason but the most likely answer, apart from
>>> slow data rate and latency when compared to a local filesystem (which,
>>> in your case on loopback, should not be an issue), is that the OS can't
>>> really use a cache for files on NFS since it has no way to know whether
>>> or not it's valid. With a lot of random-access reads and writes, that
>>> can be a HUGE slowdown, as you found.
>>>
>>>
>>> Also this:
>>> https://sqlite.org/faq.html#q5
>>>
>>> In other words, Subversion working copies on NFS are, and have always
>>> been, a bad idea; not only because of SQLite but also because
>>> Subversion's code itself relies on atomic renames, which NFS does not
>>> provide.
>>>
>>> -- Brane
>>
>> What SVN command (on command line) I should test to get a similar
>> result as from ISVNClient.getChangelists?
>
> If "adding/removing a file" is any indication, then "svn add" or "svn
> remove" should be comparable.

Sorry, this was misleading. Adding/removing a file cause a refresh of
which ISVNClient.getChangelists takes the longest time. With SmartSVN
Foundation ISVNClient.getChangelists is not invoked and hence much
faster when refreshing after a command, e.g. add or remove.

Which is the SVN command line equivalent of ISVNClient.getChangelists?

--
Best regards,
Thomas Singer
=============
syntevo GmbH
http://www.syntevo.com
http://www.syntevo.com/blog
Received on 2017-10-19 10:08:15 CEST

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