Subversion svn+ssh, sshd 100% CPU

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Subversion svn+ssh, sshd 100% CPU

Zoran Petkovic

In the past few days I have been doing extensive testing of Subversion with different clients, operating systems, client and server versions and have noticed very strange behaviour with windows clients connecting to Linux servers, hitting them with excessive CPU usage on the sshd process, where the Linux clients do not exhibit this behaviour.

 

A sample test setup is as follows:

Server Linux Ubuntu 16.04.3 LTS, OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g  1 Mar 2016, Subversion version 1.9.3 (and 1.9.7).

Client TortoiseSVN 1.9.7

 

When checking out large repositories the linux server is hit on the sshd process, the process running with 100% cpu usage. This in effect slows down the performance and ultimately the speed at which the checkout runs. Linux clients connecting to the same server do not cause this load on the server.

 

This happens even when compressions is turned off and when encryption Cyphers are changed, as well as different versions of subversion. The behaviour is identical. I'm not sure who to address for this issue as this not only happens with TortoiseSVN but with SlikSVN as well. Any direction would be appreciated.

 

Regards,

 

-- 

Zoran Petkovic

 

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Re: Subversion svn+ssh, sshd 100% CPU

Matt Simmons
Why does iostat show? Could it be that your underlying disk is io-saturated and your CPU spike is due to iowait?



On Tue, Sep 12, 2017 at 12:14 PM Zoran Petkovic <[hidden email]> wrote:

In the past few days I have been doing extensive testing of Subversion with different clients, operating systems, client and server versions and have noticed very strange behaviour with windows clients connecting to Linux servers, hitting them with excessive CPU usage on the sshd process, where the Linux clients do not exhibit this behaviour.

 

A sample test setup is as follows:

Server Linux Ubuntu 16.04.3 LTS, OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g  1 Mar 2016, Subversion version 1.9.3 (and 1.9.7).

Client TortoiseSVN 1.9.7

 

When checking out large repositories the linux server is hit on the sshd process, the process running with 100% cpu usage. This in effect slows down the performance and ultimately the speed at which the checkout runs. Linux clients connecting to the same server do not cause this load on the server.

 

This happens even when compressions is turned off and when encryption Cyphers are changed, as well as different versions of subversion. The behaviour is identical. I'm not sure who to address for this issue as this not only happens with TortoiseSVN but with SlikSVN as well. Any direction would be appreciated.

 

Regards,

 

-- 

Zoran Petkovic

 

--
"Today, vegetables... Tomorrow, the world!" 
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Re: Subversion svn+ssh, sshd 100% CPU

Johan Corveleyn-3
On Wed, Sep 13, 2017 at 7:20 AM, Matt Simmons <[hidden email]> wrote:

> On Tue, Sep 12, 2017 at 12:14 PM Zoran Petkovic <[hidden email]>
> wrote:
>>
>> In the past few days I have been doing extensive testing of Subversion
>> with different clients, operating systems, client and server versions and
>> have noticed very strange behaviour with windows clients connecting to Linux
>> servers, hitting them with excessive CPU usage on the sshd process, where
>> the Linux clients do not exhibit this behaviour.
>>
>>
>>
>> A sample test setup is as follows:
>>
>> Server Linux Ubuntu 16.04.3 LTS, OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL
>> 1.0.2g  1 Mar 2016, Subversion version 1.9.3 (and 1.9.7).
>>
>> Client TortoiseSVN 1.9.7
>>
>>
>>
>> When checking out large repositories the linux server is hit on the sshd
>> process, the process running with 100% cpu usage. This in effect slows down
>> the performance and ultimately the speed at which the checkout runs. Linux
>> clients connecting to the same server do not cause this load on the server.
>>
>>
>>
>> This happens even when compressions is turned off and when encryption
>> Cyphers are changed, as well as different versions of subversion. The
>> behaviour is identical. I'm not sure who to address for this issue as this
>> not only happens with TortoiseSVN but with SlikSVN as well. Any direction
>> would be appreciated.
>
> Why does iostat show? Could it be that your underlying disk is io-saturated
> and your CPU spike is due to iowait?

One possible explanation would be that the windows clients perform the
checkout faster than the linux clients for some reason, thus being
able to put higher load on the server, saturating its cpu or disk I/O.

Other than that I have no idea.

The Linux client you're testing is also 1.9.7?

Perhaps the windows client and the linux client are performing the
checkout in a different way for some reason (I'm thinking of the
so-called "skelta mode" vs. "bulk mode", see
http://subversion.apache.org/docs/release-notes/1.8.html#serf-skelta-default).

--
Johan
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RE: Subversion svn+ssh, sshd 100% CPU

Bert Huijben-5


> -----Original Message-----
> From: Johan Corveleyn [mailto:[hidden email]]
> Sent: donderdag 14 september 2017 22:10
> To: Matt Simmons <[hidden email]>
> Cc: Zoran Petkovic <[hidden email]>;
> [hidden email]
> Subject: Re: Subversion svn+ssh, sshd 100% CPU
>
> On Wed, Sep 13, 2017 at 7:20 AM, Matt Simmons <[hidden email]>
> wrote:
> > On Tue, Sep 12, 2017 at 12:14 PM Zoran Petkovic
> > <[hidden email]>
> > wrote:


> Perhaps the windows client and the linux client are performing the checkout
> in a different way for some reason (I'm thinking of the so-called "skelta
> mode" vs. "bulk mode", see http://subversion.apache.org/docs/release-
> notes/1.8.html#serf-skelta-default).

'Skelta vs bulk' is specific to operations over http(s), so this wouldn't apply here. The relevant part here is probably which ssh client is used here. On most *nix systems this would be openssh, while on most Windows systems I would see some putty based tools.

        Bert
>
> --
> Johan

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Fwd: Re: Subversion svn+ssh, sshd 100% CPU

Johan Corveleyn-3
In reply to this post by Johan Corveleyn-3
Forwarding to the list (Zoran, please use reply all to keep the list in cc).


---------- Doorgestuurd bericht ----------
Van: "Zoran Petkovic" <[hidden email]>
Datum: 21 sep. 2017 19:01
Onderwerp: Re: Subversion svn+ssh, sshd 100% CPU
Aan: "Johan Corveleyn" <[hidden email]>
Cc:

Correction, I meant to say KBytes/s.

--
Zoran Petkovic
Industrial Engineering Technology Pty Ltd
<a href="tel:%2B61%20413%20254%20315" value="+61413254315">+61 413 254 315 <tel:0413%20254%20315> | [hidden email]


On 21/09/2017, 4:17 PM, "Zoran Petkovic" <[hidden email]> wrote:

    My results show that Linux clients stress the server less and complete the checkout quicker (5-10% on sshd and svnserve). Windows clients connecting remotely start off fast 2000-3000kbit/s then slow down to maximum 800kbit/s, the sshd process running at 100%, while the svnserve at 5%. So, I believe it is an issue with ssh rather than svn. Skelta mode seems to refer to apache, however these clients connect over ssh.

    --
    Zoran Petkovic
    Industrial Engineering Technology Pty Ltd
    <a href="tel:%2B61%20413%20254%20315" value="+61413254315">+61 413 254 315 <tel:0413%20254%20315> | [hidden email]


    On 14/09/2017, 10:10 PM, "Johan Corveleyn" <[hidden email]> wrote:

        On Wed, Sep 13, 2017 at 7:20 AM, Matt Simmons <[hidden email]> wrote:
        > On Tue, Sep 12, 2017 at 12:14 PM Zoran Petkovic <[hidden email]>
        > wrote:
        >>
        >> In the past few days I have been doing extensive testing of Subversion
        >> with different clients, operating systems, client and server versions and
        >> have noticed very strange behaviour with windows clients connecting to Linux
        >> servers, hitting them with excessive CPU usage on the sshd process, where
        >> the Linux clients do not exhibit this behaviour.
        >>
        >>
        >>
        >> A sample test setup is as follows:
        >>
        >> Server Linux Ubuntu 16.04.3 LTS, OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL
        >> 1.0.2g  1 Mar 2016, Subversion version 1.9.3 (and 1.9.7).
        >>
        >> Client TortoiseSVN 1.9.7
        >>
        >>
        >>
        >> When checking out large repositories the linux server is hit on the sshd
        >> process, the process running with 100% cpu usage. This in effect slows down
        >> the performance and ultimately the speed at which the checkout runs. Linux
        >> clients connecting to the same server do not cause this load on the server.
        >>
        >>
        >>
        >> This happens even when compressions is turned off and when encryption
        >> Cyphers are changed, as well as different versions of subversion. The
        >> behaviour is identical. I'm not sure who to address for this issue as this
        >> not only happens with TortoiseSVN but with SlikSVN as well. Any direction
        >> would be appreciated.
        >
        > Why does iostat show? Could it be that your underlying disk is io-saturated
        > and your CPU spike is due to iowait?

        One possible explanation would be that the windows clients perform the
        checkout faster than the linux clients for some reason, thus being
        able to put higher load on the server, saturating its cpu or disk I/O.

        Other than that I have no idea.

        The Linux client you're testing is also 1.9.7?

        Perhaps the windows client and the linux client are performing the
        checkout in a different way for some reason (I'm thinking of the
        so-called "skelta mode" vs. "bulk mode", see
        http://subversion.apache.org/docs/release-notes/1.8.html#serf-skelta-default).

        --
        Johan