Comment 45 for bug 727064

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In , Tudor Bosman (tudorb) wrote :

(In reply to Ondrej Bilka from comment #29)
> Wait, do you have overlapping source and destination areas? If so then a
> backward copy is necessary.

Backward copy is often used for non-overlapping areas as it is faster on some Intel processors; see https://bugzilla.redhat.com/show_bug.cgi?id=638477#c99 for an explanation. I was pointing out that it also has the (unintended) behavior of pessimizing mmap()ed file accesses.