[vdr] Patch to avoid file system buffer trashing

Ralf Müller rmvdr at bj-ig.de
Mon Aug 22 11:17:21 CEST 2005


The day before I tried to find out if somebody ever had implemented 
something to prevent vdr to trash the file system buffers. I did this 
because I hate to wait 20 seconds for vdr to re-read my recordings 
list. So I read about the usage of O_DIRECT and the trouble with it. 
While googling about O_DIRECT I found the function posix_fadvise - 
which I had never heard about before - can help to do something similar 
without to have such an impact on the current programming scheme.

Using this function I wrote a little patch for vdr 1.3.30 - if you are 
interested have a look here:

http://vdr.unetz.com/download/patches/vdr-avoidTrashing-0.2.0-plain-1.3.30.diff.gz

The same patch against enAIO-2.5-rm-a:

http://vdr.unetz.com/download/patches/vdr-avoidTrashing-0.2.0.diff.gz

For sure the whole thing only makes sense when all programs dealing with 
video streams on a vdr do the same. So I did some first steps patching 
noad. I'm not finished with it - there seems to be a read() I missed.
Anyway - the preliminary patch for noad 0.6.0 can be found here:

http://vdr.unetz.com/download/patches/noad-avoidTrashing-0.0.1.diff.gz

Further candidates for posix_fadvise are mkisofs and the burn-plugin.

Regards
Ralf Müller

-- 
Van Roy's Law: -------------------------------------------------------
       An unbreakable toy is useful for breaking other toys.



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