[mythtv-users] system profiling / cpu usage revisited
Aike Terjung
aike at terjung.net
Fri Jun 20 01:18:09 EDT 2003
sorry if i understand somthing wrong, but my english is not the best.
have you activated the DMA Mode for the harddisks?
cu Aike
Am Donnerstag, 19. Juni 2003 23:06 schrieb Brian Lalor:
> Ok, I've been doing some poking around with iostat and vmstat. I changed
> my settings so that I'm now doing MPEG-4 encoding (exact params not
> important ATM). My CPU's at ~100% most of the time that this recording is
> taking place. iostat shows:
>
> Time: 03:44:55 PM
> avg-cpu: %user %nice %sys %idle
> 99.10 0.00 0.70 0.20
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s \
> avgrq-sz avgqu-sz await svctm %util
> /dev/hda 0.00 46.00 0.00 8.80 0.00 438.40 0.00 219.20 \
> 49.82 4294697.37 0.80 113.64 100.00
> /dev/hda5 0.00 45.00 0.00 6.40 0.00 411.20 0.00 205.60 \
> 64.25 0.06 0.94 0.47 0.30
>
> Top shows mythbackend as the biggest CPU hog currently (of course):
> PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
> 29384 myth 9 0 41700 31M 3360 S 98.3 6.3 17:47 0
> mythbackend
>
> Let me just preface my remarks by saying that I don't really know the first
> thing about the workings of the kernel and system tuning, but I really want
> to get this sorted out, as I see many people having these issues. It may
> be a bad choice of hard drive or motherboard, but I want to get to the
> bottom of it.
>
> First, as iostat shows above (sorry for the line-wrapping), my CPU's maxxed
> out by user processes, not by the kernel. Doesn't this mean that it is in
> fact mythbackend that is tying up the CPU by compressing the data, rather
> than (if %sys were very high) that the kernel was spending all of its time
> in I/O routines?
>
> Second, the wkB/s column shows that I'm dumping about 205kB to the
> partition (/dev/hda5 is where my recordings go) a second (or around 1 meg
> every four seconds). hdparm tells me my disk throughput is around 30
> meg/s, so that should be plenty. I don't know what to make of the write
> queue information.
>
> Lastly, here's some vmstat info:
> procs memory swap io system
> cpu r b w swpd free buff cache si so bi bo in cs us
> sy id 1 0 0 17228 4408 41016 365680 0 0 0 198 164 296
> 100 0 0
>
> Again we see my CPU maxxed, plenty of un-used memory, a bunch of blocks
> being written to the disk and a butt-load of context switches in the last
> two seconds (time since the last report). Does that seem like a lot? I
> dunno. Maybe someone else can do a similar analysis on a similar machine
> that can do the MPEG-4 encoding without breaking a sweat? Here's a
> breakdown of my hardware again:
> Asus A7V8X-X motherboard (via chipset)
> AMD AthlonXP 1700+
> 512MB PC2700 DDR RAM
> WinTV-dbx tuner card
> 120GB 7200RPM Hitachi IDE drive
> linux kernel 2.4.21 compiled exactly for my hardware (mostly as reported
> via lspci)
>
> Collecting data is easy. Analyzing it is hard. :-)
>
> Thanks,
> B
More information about the mythtv-users
mailing list