Re: [PATCH 1/2] Introduce copy_user_handle_tail routine

[Vitaly Mayatskikh]

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:

> Now, the stuff that comes *before* that point is the "try to fix up one 
> byte at a time" thing, which I'd like to be simple and dumb. At least to 
> start with.

Just to be clear: do these patches are good enough now (to start with)?
Or, may be, it needs to be further improved?

> Of course, I also suspect that *eventually* we might want to make it 
> smarter and more complex. For example, while performance isn't a primary 
> issue, we might want to eventually avoid having to do _two_ faults (once 
> in the fast unrolled or word-at-a-time loop, and once in the byte-for-byte 
> one), by limiting the byte-for-byte one to be within a page, but that 
> would be a "future enhancement" thing.

Btw, how much does it cost to CPU to do a fault? Can it be compared with
average time of find_vma()?

-- 
wbr, Vitaly
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