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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Hello,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">I have one query on the behaviour I am overserving with systemd service.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Below are the contents of service file,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""># cat</span><span style="font-family:"Arial",sans-serif">
</span><span style="font-family:"Courier New"">/usr/lib/systemd/system/qs.service</span><span style="font-family:"Arial",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[Unit]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Description=init script<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">After=network.target<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[Service]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">ExecStartPre=/bin/sh /usr/local/cmcluster/bin/realtimeslice.sh -s /usr/lib/systemd/system/qs.service<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">ExecStart=/usr/local/qs/bin/qs<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Type=simple<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">[Install]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">WantedBy=multi-user.target<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">What </span><span style="font-family:"Courier New"">realtimeslice.sh</span><span style="font-family:"Arial",sans-serif"> does is to identify a slice having RT quantum (cpu.rt_runtime_us) as 950000.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Once the slice is identified the service attaches the binary mentioned in ExecStart to that slice.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">This is done because binary(</span><span style="font-family:"Courier New"">/usr/local/qs/bin/qs)</span><span style="font-family:"Arial",sans-serif"> tries to set realtime priority.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Now coming to the issue which I am facing,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">Suppose I have 2 slices, A.slice (cpu.rt_runtime_us value = 950000) and B.slice (cpu.rt_runtime_us value = 0)<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">Currently the service qs.service is attached to A.slice
<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">Now I changed cpu.rt_runtime_us values for these slices: A.slice to 0 and B.slice to 950000.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">4.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">When I restart the service, ExecStartPre (i.e realtimeslice.sh) determines that B.slice is eligible slice and it updates the slice name in the configuration files and in drop-ins.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">5.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">But Binary at ExecStart still doesn’t see the updated slice info and fails to set the realtime priority.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="font-family:"Arial",sans-serif"><span style="mso-list:Ignore">6.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-family:"Arial",sans-serif">If I restart the service again it is working fine and binary is able to set the realtime priority.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Is it that systemd at its invocation caches the all the information (including slice values) and uses those values for ExecStart[Pre] ? Because in the next run it is working fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Is there a way reload/refresh the settings done at ExecStartPre, so that it will reflect at ExecStart.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Thanks & Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Hari.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
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