Hi,
we have discussed this subject here before.
I believe we consent that the main reason for the big delays
when opening the recordings menu is the fact that vdr reads
and writes huge amounts of data from/to the nnn.vdr files,
the kernel tries to cache these, thus moving much more useful
stuff (like cached directory entries and cached small files)
out of the memory cache.
It usually makes no sense at all to cache the nnn.vdr files,
as they normally are read/written only once.
I recently found out that kernels > 2.4.9 seem to have exactly
the solution we were looking for.
From "man 2 open":
O_DIRECT
Try to minimize cache effects of the I/O to and
from this file. In general this will degrade per
formance, but it is useful in special situations,
such as when applications do their own caching.
File I/O is done directly to/from user space
buffers. The I/O is synchronous, i.e., at the com
pletion of the read(2) or write(2) system call,
data is guaranteed to have been transferred.
Transfer sizes, and the alignment of user buffer
and file offset must all be multiples of the logi
cal block size of the file system.
This flag is supported on a number of Unix-like
systems; support was added under Linux in kernel
version 2.4.10.
A semantically similar interface for block devices
is described in raw(8).
I guess a patch that uses this should be trivial.