On Wed, 2007-07-25 at 12:26 +0200, Andi Kleen wrote: > > Plan is fixed array or 4 or maybe 8 entries (pointers), that shouldn't > > be -too- bad. The code path I'm a bit worried about is > > Yep. > > > unmap_mapping_ranges() which goes into zapping page tables from deep > > within filesystems. > > Your aim is to conserve stack space? > The worst case has to work without overflow anyways, so using VLAs don't > help you. Just allocate the largest size you can safely afford. > > This is also easier to test; if it is too large it is better when > the overflow triggers always. > > They are more useful in user space with larger stacks when you don't > know the maximum size.
In fact, i discussed with peter and I think the best is to only have one entry in the stack mmu_gather structure. If we fail to allocate a page to batch entries, we flush that one and steal it :-) Then we have a page to gather more. I'll give that a go tomorrow, I got delayed by some stupid HW issues today. Cheers, Ben. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
