Re: 2.4: NFS client kmapping across I/O

[Rik van Riel]

On Tue, 29 Jan 2002, Hugh Dickins wrote:
> On Mon, 28 Jan 2002, Xeno wrote:
> >
> > Now I also have time to mention the other NFS client issue we ran into
> > recently, I have not found mention of it on the mailing lists.  The NFS
> > client is kmapping pages for the duration of reads from and writes to
> > the server.  This creates a scaling limitation, especially under
>
> You're right that kmap users should avoid holding them for very long,
> I'd certainly not discourage anyone from pursuing that effort.

Things like this would be fixed by having a kmap variant
which maps the pages into process-private space, kind of
like kmap_atomic(), but into a (4 MB sized?) part of
address space which is only visible within this process.

This would mean that each process can have a few MB of
kmap()d pages ... should be nice for things like having
copy_{to,from}_user "cache" the hot pages while keeping
longer term mappings from filling the global pool.

regards,

Rik
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