It is zero-copy
Posted Apr 8, 2006 18:26 UTC (Sat) by axboe
In reply to: It is zero-copy
Parent article: Two new system calls: splice() and sync_file_range()
Copy is in quotes, because it's not the CPU doing the copy. Which is what is interesting, and why zero-copy just means zero CPU copies. That is where you pay the cost, at least in CPU cycles and potentially also in cache. So zero-copy definitely isn't just a play on words. It may sometimes be used in silly marketing ways, but if you are CPU bound it makes all the difference in the world that the CPU doesn't have to touch the data.
And yes, the normal copy is indeed two copies, to and from kernel/user space.
You can continue talking if you want, but don't expect a response from me.
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