Nachricht geschrieben von "Stephen C. Tweedie"
>
> > Maybe you meant that fdatasync() will keep latency low in a single
> > threaded model, but these latencies are way too big , and the only
> > solution is the 2 thread mode. The problem is that when you do
> > harddisk recording, in some cases, you don't know in advance the
> > length of the recording, therefore you must write to the disk
> > dynamically without prealloc or writing NULLs to the file, even if
> > you have to sacrifice a bit of performance.
>
>No, that's not what I'm talking about. I'm just talking about disk
>performance. If you use regular fdatasync then you avoid letting the
>kernel accumulate a huge queue of dirty writeback buffers in the
>buffer cache. If you don't use synchronous writes, then your
>writeback queue grows to the point that when the bdflush task
>eventually decides to flush things out, it can clog the disk request
>queues for a substantial period.
Best thing would be to bypass the BufferCache. The Data written
will not be reused very soon do forget it. Is there a (posix) way to
bipass the BufferCache??
I do this allready inside the kernel, but I like to throw out some
processes to cold userland :).
Jens Michaelsen
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