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On 14/07/13 11:57, Christian Hack wrote:<br>
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<p class="MsoNormal">Hi everyone<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Having some issues with my latest
incarnation of MythTV.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It’s mythbuntu based from 12.04 and updated
to the latest everything. Mythbackend reports as “mythbackend
version: fixes/0.25 [v0.25.3-48-g3a1eff8] <a
moz-do-not-send="true" href="http://www.mythtv.org">www.mythtv.org</a>”<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">CPU is an i3-2100 on an ASRock B75-PRO3-M
motherboard, 3GB RAM, 3TB main drive and a couple of other
smaller ones. Playback is VDPAU which works OK.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">hdparm –t reports speeds of 60-70MByte/sec
no problem on all drives and only 4-5MB/sec when recording as
expected. There seems to be no actual issue with recordings.
There are no corruptions or dropouts ever that I notice.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Tuners are two dual tuner “USB Lifeview TV
Walker Twin” devices for a total of 4 DVB-T tuners. I have 4
virtual tuners on each although rarely do they ever get
exercised to the full extent. Helpful for overlapping
recordings though.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My problem is that when a recording is
running I’m seeing quite high CPU usage from mythbackend. A HD
show (1440x1080) will take 60-80% CPU per recording. When a
couple of recordings are going I see something like the top
output below (2 x HD and 1 x SD recordings) with a load
average to match. DVB-T recordings really shouldn’t need
much/any CPU. Load average occasionally even gets up to 8-10
or more.<o:p></o:p></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"">top - 20:46:06 up 1 day, 8:55, 3 users, load
average: 5.29, 5.88, 6.49<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New"">Tasks: 211 total, 2 running, 208 sleeping, 1
stopped, 0 zombie<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New"">Cpu(s): 20.4%us, 29.0%sy, 0.1%ni, 45.4%id,
5.1%wa, 0.0%hi, 0.0%si, 0.0%st<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New"">Mem: 3023632k total, 2953156k used, 70476k
free, 12280k buffers<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New"">Swap: 9765884k total, 447804k used, 9318080k
free, 1418564k cached<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""> PID USER PR NI VIRT RES SHR S %CPU
%MEM TIME+ COMMAND<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 4197 mythtv 20 0 2927m 121m 6040 S 202
4.1 1028:10 mythbackend<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 8672 mythtvus 20 0 3007m 247m 30m S 4
8.4 57:35.85 mythfrontend.re<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 1627 root 20 0 188m 51m 23m S 1
1.7 4:59.26 Xorg<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 595 root 20 0 0 0 0 S 0
0.0 0:20.11 jbd2/sda3-8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 1419 mysql 20 0 2434m 152m 4212 S 0
5.2 75:42.51 mysqld<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 1462 root 20 0 32908 604 504 S 0
0.0 3:47.02 lircd<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier
New""> 2705 nobody 20 0 16972 704 636 S 0
0.0 5:21.88 LCDd<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This in turn really slows the whole system
down which is a problem since it’s an all in one machine.
Often it will drop out with “irrecoverable recorder error”
back to the recordings screen. The recording doesn’t seem at
affected though and I just start it again and it works. 1000
minutes over 32 hours is a fair bit of CPU time just for
recordings. Doing something like moving a file from one disk
to another seems to make it even worse (but I get a get 60-70
MByte/sec transfer speeds)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I only have a 1 instance of mythcommflag
running at once but even killing that one makes no difference.
It’s a separate process anyway.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This didn’t happen previously (was using
Mythdora 12.25) on the same tuners (same CPU but different
motherboard).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Otherwise it works quite well. Is this CPU
usage likely to be MythTV building the recordedseek table for
the recordings that are running? That’s about all I can think
of. Is it normal now? <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Sorry about the length - tried to include
as much detail as I can. I don’t see much that is helpful in
any logs.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any ideas? Is this just “normal”? With a
few recordings it’s a bit painful to use particularly when it
keeps dropping out of playback. The machine is not a
powerhouse but should be easily capable of what I’m doing.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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</blockquote>
<br>
That does sound a little high to me, but it could just be due to the
fact that USB relies on the CPU for a lot (hence it's cheap).<br>
<br>
As another data point for comparison, my system is sitting at around
16-19% while recording 2 SD DVB-T programmes from a Nova T-500.
This with a Celeron E3400 CPU, and writing to a mirrored pair of
SATA drives.<br>
<br>
thanks,<br>
Alex<br>
<br>
P.S. the Nova T-500 is actually a USB tuner, even though it looks
like a PCI card -
<a class="moz-txt-link-freetext" href="http://www.linuxtv.org/wiki/index.php/Hauppauge_WinTV-NOVA-T-500">http://www.linuxtv.org/wiki/index.php/Hauppauge_WinTV-NOVA-T-500</a><br>
<br>
<pre class="moz-signature" cols="72">--
Alex Tomlins
Email/Jabber: <a class="moz-txt-link-abbreviated" href="mailto:alex@tomlins.org.uk">alex@tomlins.org.uk</a>
There are two kinds of people in the world: those who finish what they started
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