On Wed, Feb 07, 2007 at 12:47:17PM -0800, Nishanth Aravamudan wrote:
> On 07.02.2007 [14:27:10 -0600], Adam Litke wrote:
> > On Wed, 2007-02-07 at 11:37 -0800, Nishanth Aravamudan wrote:
> > > @@ -831,6 +832,57 @@ static void remap_segments(struct seg_info *seg, int
> > > num)
> > > /* The segments are all back at this point.
> > > * and it should be safe to reference static data
> > > */
> > > +
> > > + /*
> > > + * This pagecache dropping code should not be used for shared
> > > + * segments. But we currently only share read-only segments, so
> > > + * the below check for PROT_WRITE is implicitly sufficient.
> > > + *
> > > + * Note: if minimal_copy is enabled, it is overkill to try and
> > > + * save huge pages here, as we will end up using more than
> > > + * normal anyways. Also, due to limitations on certain
> > > + * architectures, we would need to avoid prefaulting in the
> > > + * extracopy area so as to not use an inordinate number of huge
> > > + * pages.
> > > + */
> > > + if (minimal_copy) {
> >
> > Now the added indent is really making me want to say this is getting
> > large enough to want its own function. I think the previous patch to
> > store the extracopy info in the seg array allows you to pass only one
> > param (the seg array) into the drop_cache() function.
>
> heh, yep, updated again:
>
> Author: Nishanth Aravamudan <[EMAIL PROTECTED]>
> Date: Mon Feb 5 14:22:02 2007 -0800
>
> elflink: drop hugepage cached pages for writable segments
>
> We currently use extra hugepages for writable segments because of the
> first MAP_SHARED mmap() which stays resident in the page cache. Use a
> helper function to force a COW for the filesz portion, as well as the
> extracopy area, of writable segments and then fadvise() to drop the page
> cache pages while keeping our PRIVATE mapping. This is mutually
> exclusive to segment sharing, but is also orthogonal in code because we
> only allow sharing of read-only segments. Also, if the minimal_copy
> algorithm is disabled, we disable this optimization.
>
> Signed-off-by: Nishanth Aravamudan <[EMAIL PROTECTED]>
Looks reasonable. However, we probably don't want to apply this patch
for real until the kernel bug which makes the fadvise() screw up the
reserved pages accounting is fixed.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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