On January 29, 2002 06:25 pm, Rik van Riel wrote:
> On Tue, 29 Jan 2002, Oliver Xymoron wrote:
>
> > Daniel's approach seems to be workable (once he's spelled out all the
> > details) but it misses the big performance win for fork/exec, which is
> > surely the common case. Given that exec will be throwing away all these
> > mappings, we can safely assume that we will not be inheriting many shared
> > mappings from parents of parents so Daniel's approach also still ends up
> > marking most of the pages RO still.
>
> It gets worse. His approach also needs to adjust the reference
> counts on all pages (and swap pages).
Well, Rik, time to present your algorithm. I assume it won't reference
counts on pages, and will do some kind of traversal of the mm tree. Note
however, that I did investigate the class of algorithm you are interested in,
and found only nasty, complex solutions there, with challenging locking
problems. (I also looked at a number of possible improvements to virtual
scanning, as you know, and likewise only found ugly or inadequate solutions.)
Before you sink a lot of time into it though, you might add up the actual
overhead you're worried about above, and see if it moves the needle in a real
system.
-- Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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