Re: [PATCH/RFC] A method for clearing out page cache

[Andrew Morton <akpm@osdl.org>]

Paul Jackson <pj@sgi.com> wrote:
>
> Andrew wrote:
> > sys_free_node_memory(long node_id, long pages_to_make_free, long what_to_free)
> > ...
> > - To make the syscall more general, we should be able to reclaim mapped
> >   pagecache and anonymous memory as well.
> 
> sys_free_node_memory() - nice.
> 
> Does it make sense to also have it be able to free up slab cache,
> calling shrink_slab()?

Yes, I suggested that slab be one of the `what_to_free' flags.  (Some of
this may be tricky to implement.  But a good interface with an
initially-crappy implementation is OK ;)

> Did you mean to pass a nodemask, or a single node id?  Passing a single
> node id is easier - we've shown that it is difficult to pass bitmaps
> across the user/kernel boundary without confusions.  But if only a
> single node id is passed, then you get the thread per node that you just
> argued was sometimes overkill.

I meant a single node ID.  With a bitmap, the kernel needs to futz around
scanning the bitmap, launching kernel threads, etc.

I'm proposing that there be no kernel threads at all.   If you have four nodes:

for i in 0 1 2 3
do
	call-sys_free_node_memory $i -1 -1 &
done

> I'd prefer the single node id, because it's easier to get right.

yup.