On Tue, Mar 13, 2001 at 19:41:50 -0600, Rohit Rakshe wrote:
> Hello,
>
> I am sure people have thought about this one, but just that I could not
> find any discussions about it:
>
> Consider a server which receives data over network, does some operations
> on the data and sends it back over the network. The kernel could spent
> most of its time copying data to and from user space. (the operations are
> performed in the user space).
>
> The following can be done to avoid this overhead:
>
> Say, I want to copy a page from user space to kernel, I can just pin it in
> physical memory; then attach it to kernel page table. (similar thing for
> other way round).
>
> Is this kinda thing implemented ? If not, is it feasible ?
Yes, it has been done. See:
http://people.FreeBSD.org/~ken/zero_copy/
The version of the patches linked off the page isn't the latest, the latest
is here:
http://people.FreeBSD.org/~ken/zero_copy/zero_copy.diffs.20010124
Those diffs are against -current as of January 24th. I can probably supply
diffs against a newer version of -current if you need 'em.
The NFS code isn't ready for prime time, I need to rip that out and clean
up some mutex issues before the code can go into -current.
Ken
--
Kenneth Merry
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