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From: Johan Corveleyn <jcorvel@gmail.com>
Date: Thu, 14 Sep 2017 22:10:16 +0200
Message-ID: <CAB84uBWD0_8WcVPUtk-ujrOZHYxr3C5DW5au3xS--r83aKz-kw@mail.gmail.com>
Subject: Re: Subversion svn+ssh, sshd 100% CPU
To: Matt Simmons <bandman@gmail.com>
Cc: Zoran Petkovic <zoran@ietcombustion.com>,
	"users@subversion.apache.org" <users@subversion.apache.org>
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archived-at: Thu, 14 Sep 2017 20:10:49 -0000

On Wed, Sep 13, 2017 at 7:20 AM, Matt Simmons <bandman@gmail.com> wrote:
> On Tue, Sep 12, 2017 at 12:14 PM Zoran Petkovic <zoran@ietcombustion.com>
> 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