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| Mythtv bottleneck http://forum.linhes.org/viewtopic.php?f=6&t=16344 |
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| Author: | beerisgoodmate [ Thu Sep 06, 2007 10:41 pm ] |
| Post subject: | Mythtv bottleneck |
My mythbox isn't as snappy as I would like. And I'm considering upgrading. Specifically, changing channels seems to take a while, and it seems to spend a bit of time writing to the HD sometimes. Current system; Sempron 754 3200 512Mb DDR 400 128Mb gf4000 AGP 200Gb samsung PATA Leadtek DTV1000T Asus K8N R5E50 I realize this is pretty low spec. Though I would have though it would be sufficient. Is upgrading the ram & cpu etc going to improve channel changing itc? What about the HD? Or is it due to the dvb card? I would hate to upgrade and get little improvement! Cheers |
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| Author: | tjc [ Thu Sep 06, 2007 11:01 pm ] |
| Post subject: | |
See the MythTV FAQ for this oldie but goodie: http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions#When_using_live_TV.2C_why_is_there_a_delay_between_the_moment_I_change_the_channel_and_the_time_the_channel_actually_changes.3F |
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| Author: | cecil [ Thu Sep 06, 2007 11:10 pm ] |
| Post subject: | |
I'd say we need a better definition of "snappy"... |
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| Author: | beerisgoodmate [ Thu Sep 06, 2007 11:29 pm ] |
| Post subject: | |
thanks tjc, Would a faster HD noticeably speed things up? What about faster cpu and more ram speed, higher FSB etc? Some times it sits there for a few seconds with rapid HD activity, could this be due to running out of ram and using swap? |
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| Author: | tjc [ Thu Sep 06, 2007 11:33 pm ] |
| Post subject: | |
For HDTV 1Gb is better, but for SDTV 512Mb is plenty. I've got roughly the same class of CPU and RAM and my performance is fine. The disk buffering time delays are exactly that however, timed delays. Faster CPU and RAM more aren't going to reduce them below those fixed timer values. |
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| Author: | beerisgoodmate [ Thu Sep 06, 2007 11:57 pm ] |
| Post subject: | |
thanks, thats what I was wondering. I'm still a little sus that the HD is slowing things down. Simply because I can hear and see how busy it is. Do you think a faster HD dedicated to /myth partition might help? |
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| Author: | mogator88 [ Fri Sep 07, 2007 1:52 am ] |
| Post subject: | |
We have similar systems. Your CPU is the better end of socket 754. A Sempron is an Athlon CPU with smaller cache. I bet an extra 512 RAM will help though. I just replaced my Sempron 2800 with an Athlon 3200. The menus are faster, but watching recordings is basically the same. I have 1gb. Hard to say what a faster disk will do, because the HD data stream tops out at less than 20mbps. FWIW when watching recordings I get an occassional "pause", but also I watch everything at 1.15x speed, minimum 
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| Author: | Human [ Fri Sep 07, 2007 8:58 am ] |
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cecil wrote: I'd say we need a better definition of "snappy"...
I'll see if NIST has one we can reference. |
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| Author: | beerisgoodmate [ Fri Sep 07, 2007 9:26 pm ] |
| Post subject: | |
Quote: I'd say we need a better definition of "snappy"... dictionary.com's 4th entry is sufficient: Quote: 4. quick or sudden in action or performance.
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| Author: | nigelpearson [ Fri Sep 07, 2007 11:58 pm ] |
| Post subject: | |
beerisgoodmate wrote: Some times it sits there for a few seconds with rapid HD activity, could this be due to running out of ram and using swap?
Unlikely. My home Myth box originally had 256MB (R4V4?). It never used swap very much. Newer MythTV versions, and complicated menu themes, use a little bit more RAM, but not a lot. Changing channels in LiveTV just takes a long time. A fast hard disk, or a faster filesystem, helps a little bit. Turning down the "HD Ringbuffer size" helps a tiny bit (if it is ridiculously large). |
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| Author: | Greg Frost [ Sat Sep 08, 2007 2:48 am ] |
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I have a default partition setup (ext3 for /myth) and when files are deleted, it can cause significant pauses. Is it possible that it is shows auto-expiring that are causing the pauses? Is your HD almost full? I have heard some claim that changing the filesystem type for the /myth partition to a filesystem with snappier deleting of large files can help in this regard. |
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| Author: | beerisgoodmate [ Sat Sep 08, 2007 11:47 pm ] |
| Post subject: | |
hmmm, I added a 320Gb seagate SATA (limited to sataI), formated as one XFS partition and set the partition to store tv. Now my channel changes are slower! I also added a DTV2000H card at the same time though. And I'm not sure if things are quite right. Old channel changes on DTV1000T ~3.6 s New channel changes DTV2000H ~4.4 s New channel changes DTV1000T ~6s Not sure if everything is set up correctly with the new card and remote yet... But I think those numbers are ok. edit: I think some of the slowdown was changing myth's tv partition, it kept looking for expired recordings to delete. I fixed this, this improves speed a little, but it is still slower. |
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