readv: parallel or sequential?

Peter Schuller peter.schuller at infidyne.com
Thu Dec 20 15:51:42 PST 2007


> multiple reads and writes to the same file *From different file
> descriptors* (same process or not) might proceed in "parallel" but readv
> and writev will be implemented serially to the filesystem. now IF THE
> FILESYSTEM IS NOT DOING SYNCHRONOUS DISK ACCESSES the reads and writes
> might proceed in parallel or be grouped, clustered or otherwise rearanged.

If the original claims were just as applied to readv/writev, I don't really 
have a problem since there is no guarantee that it will be performed in 
parallel (though even then, assuming non-synchronous writes, it would 
certainly be nice if it did pass it along to the device layer in a fashion 
that allowed concurrency).

But when I/O is clearly being done with the intent of concurrency (by using 
AIO or by performing the I/O in different threads/processes), it is more 
important.

-- 
/ Peter Schuller

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