[Freeswitch-users] FS priority

[Bote Man]

I'm not sure how much nice level matters compared to scheduler priority. I
ran a series of tests to find out what Priority and Nice level are reported
by the 'top' utility.

I ran the first 6 tests by using systemd to start FreeSWITCH, 3 times as
user root with each of the FS priority flags, then 3 times as user
freeswitch with each of the FS flags. Then I repeated that block of tests
from the command line, 3 flags as root, 3 flags as freeswitch. You won't
believe what happened next!

systemd starting FreeSWITCH as 'RUNAS' user with 'FLAG' command line
priority flags to FS results in top showing priority 'PRI', nice level
'NICE' on a month-old install of Debian 8 on a bare metal Dell R320 server.

RUNAS    FLAG    PRI    NICE
root         -rp         -2      -10
root        -np         39      19
root         -lp         39      19

fs            -rp         -2       19
fs            -np        39      19
fs            -lp         39      19

Run as root from command line
root         -rp         -2     -10
root         -np        20      0
root         -lp         39     19

Run as su=freeswitch from command line
fs            -rp        20      0
fs            -np       20      0
fs            -lp        39     19

Most processes show Priority of 20 so I assume that is considered "normal".

So it looks like the only way to get truly higher priority for a process is
to run it as root, which I expected. Once the scheduler priority is at -2
(higher priority) I don't know whether the nice level even matters.

For now, the systemd unit file that I posted on Confluence runs as the
freeswitch user so even with the -rp flag to FreeSWITCH it gets niced down
to 19 which is the lowest level available for nice. Does this matter?

Is there a serious security concern running FreeSWITCH as root?

Thanks.

Bote


On Fri, Sep 4, 2015 at 3:38 PM, Bote Man <bote_radio at botecomm.com> wrote:

> Thanks for that. I was under the impression that systemd was throwing
> FreeSWITCH into the generic scheduling group and starving it of resources
> as a result, but when I manually ran ./freeswitch as root it still showed
> the same values.
>
> Running FS manually with -np yielded pri=20 nice=0 and System Monitor
> reports priority "normal"
>
> Running FS manually with -rp yielded pri=-2 nice=-10 and System Monitor
> reports priority "very high", same results as when FS was started without
> any priority switch on the command line.
>
> BUT! When I start FS with systemd it maintains priority=-2 but nice all
> the way down to 19 which is why System Monitor reports "very low". This
> happens even with the -rp switch specified in the unit file.
>
> I don't know how scheduling priority and nice level interact on Debian,
> but it looks like I have a new research project for this weekend, assuming
> this is truly something to be concerned about. Or is it?
>
> Thanks for the tips. I will report my findings to the list if I discover
> anything substantive.
>
> Bote
>
>
>
>
>
> On Fri, Sep 4, 2015 at 2:02 PM, Shaun Stokes <
> shaun.stokes at itec-support.co.uk> wrote:
>
>> Hi Bote,
>>
>> I believe priority works in a similar way to metric (i.e. lower comes
>> first), so -20 (most favorable scheduling) to +19 (least favorable
>> scheduling).
>>
>> -rp                    -- enable high(realtime) priority settings
>> -lp                    -- enable low priority settings
>> -np                    -- enable normal priority settings (system default)
>>
>> Source: https://wiki.freeswitch.org/wiki/Command_line
>>
>> Hope this helps.
>>
>> Thanks,
>> Shaun
>> ------------------------------
>> *From:* freeswitch-users-bounces at lists.freeswitch.org [
>> freeswitch-users-bounces at lists.freeswitch.org] on behalf of Bote Man [
>> bote_radio at botecomm.com]
>> *Sent:* 04 September 2015 15:54
>> *To:* FreeSWITCH Users Help
>> *Subject:* [Freeswitch-users] FS priority
>>
>> I’m trying to set the priority on a new FreeSWITCH installation built
>> from master on Debian 8 running on bare metal. It is currently running at
>> “very low” priority according to Resource Monitor in the GUI and ‘top’
>> reports FS is running at priority = -2 (that’s negative two) and nice = 19
>>
>>
>>
>> So with the way FreeSWITCH is now launched by systemd is it considered a
>> service or a user application that is simply run in the background?
>>
>>
>>
>> This affects how systemd treats its control groups and priority and how I
>> will go about troubleshooting this.
>>
>>
>> Thanks.
>>
>>
>>
>> Bote
>>
>>
>>
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