On 09/05/2015 04:33 AM, Al Viro wrote:
> On Fri, Sep 04, 2015 at 04:25:27PM -0600, Andreas Dilger wrote:
>
>> This is a bit of a surprising result, since in my testing in the
>> past, copy_{to/from}_user() is a major consumer of CPU time (50%
>> of a CPU core at 1GB/s). What backing filesystem did you test on?
>
> While we are at it, was cp(1) using read(2)/write(2) loop or was it using
> something else (sendfile(2), for example)?
cp uses a read / write loop, and has some heuristics for guessing an optimum buffer size.
Anna
>
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