[linux-dvb] Re: Bad pervormance with reiserfs

[Christoph Ackermann <ackermann@cms.tecmath.com>]

Hello List.

I tried out several ´file_readahead´ settings for my vdr-machine running
with ReiserFS, Driver 0.82 and vdr 0.72 - I am a little bit busy, to set
up the newest possible version. Sorry!

Hardware: K6II266/128MB/Quantum-LCT20-40GB/2DVB-S

Initial value by the system for ´file_readahead´ is 124
(K2.2.1x/SuSE6.4). With these value the playout of vdr was a little
inadequate, especially at panning scenes. I thought it was a problem of
the very slow but amazing silent Quantum disk LCT20 (yes, DMA
enabled!!!). 
So i tried values between 128 and 1024 and i found out for this
configuration ´256´ is the best. So the disk is reading for a short
time(~0.1s) about each second. The playback is VERY SMOOTH and i have
not seen any jitter effects caused by the diskaccess.

ERRORS CAUSED BY A BAD MULTIPLEXING ARE NOT IMPROVED BY THIS
MODIFICATION !!!

Also i think you have to test it for each configuration, to find your
´own´ value. 
Values larger than 256 causes a malfuncion in the cutting thread. With
´512´ you need about four times longer than ´256´ for a cut!

So the next step ist to upgrade to driver 0.9x and vdr 0.8x, maybe if
´remultiplexing´ is integrated within the vdr recording thread.


*** Always nice recordings and free disk space ***

   Christoph



Matthias Weingart wrote:
> 
> On Fri, 18 May 2001, Bernhard Baptist wrote:
> 
> > hello
> >
> > because of any hints in this mailinglist, I had dealed arround with
> > reiserfs for use with the VDR.
> > But the result was not very good.
> >
> > By using ext2 for the videopartition of VDR, absolut no problems. But
> > with reiserfs on the same hardware there were a lot of sound-dropouts
> > and video-distortion - If there were fast movements in the video.
> > Had anyone made the same experience or had i made a mistake
> > (linux-newbie).
> 
> I am using reisefs too (Athlon 800) and wondered why I have so many video
> and audio distortions; never tried ext2fs; maybe I should switch to ext2fs
> too...
> 
> btw. I checked the read ahead buffer of my ide drive:
> cat /proc/ide/ide0/hda/settings
> name                    value           min             max mode
> ----                    -----           ---             --- ----
> breada_readahead        4               0               127             rw
> current_speed           66              0               69              rw
> file_readahead          0               0               2097151         rw
> init_speed              12              0               69              rw
> io_32bit                0               0               3               rw
> max_kb_per_request      128             1               127             rw
> multcount               8               0               8               rw
> using_dma               1               0               1               rw
> 
> This settings seems to be independant from the filesystem. (maybe the
> filesystem does not implement any "read ahead" ...).
> I see that file_readahead is set to 0 at my machine; not good for vdr I
> think. I will try other settings, hope this will improve the playback
> quality and will not destroy my harddisc :-/
>  echo "file_readahead:256" > settings
> 
>         Matthias
> 
________________________________________________________________________

Christoph Ackermann                                    ] t e c m a t h [
System Integration Engineer          Content Management Systems Division
phone +49 6301 606-200      Sauerwiesen 2, 67661 Kaiserslautern, Germany
fax   +49 6301 606-209                            http://www.tecmath.com
________________________________________________________________________


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