[linux-dvb] Re: Bad pervormance with reiserfs

[Matthias Weingart <matthias@pentax.boerde.de>]

To complete it with my experiences (see below my first posting): 
Readahead can be set only to off (=0) or on (>0 any value greater 0 works)
with my maxtor drive (readahead is set for the ide drive and depends
on the drive used? is this true?). With any value greater 0 it behave the
same: on playing a video the harddisk is accessed every 2..5 seconds
(hd-led) but sometimes harddisc transfer "hangs" for a short time and the
resulting video gap is visible (picture is frezed for one second). So
readahead enabled with reiserfs is worse!

        Matthias

On Mon, 11 Jun 2001, Christoph Ackermann wrote:

> 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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