On Wed, 2006-09-13 at 08:06 -0400, Hubertus Franke wrote: > Martin Schwidefsky wrote: > > On Tue, 2006-09-12 at 21:29 -0400, Rik van Riel wrote: > > > >>Note that the transition _to_ volatile can also be batched > >>and done somewhat lazily. For frequently mmaped pages that > >>could end up saving us the transition the other way, too... > > > > > > That would be helpful, only how to do it? We need some sort of list or > > array where to store the pages that should be made volatile. The main > > problem that I see is that you have to remove a page that is freed from > > the list/array again, otherwise you would end up with a non page-cache > > page being made volatile. That makes using per-cpu arrays hard since a > > page can be freed on another cpu. > > > > > Martin. the point was that pages > which are in the hold/cold lists are technically free. > However we keep them stable. > When the hot/cold list is spilled back to the buddy allocator > we make them volatile in buld (i.e. through the array). You mean unused. > So we only build the array for the duration of the bulk-release > to the buddy allocator (and potentially the other way as well). > Hence there is no "state" to maintain or track for the array. > Pages in the hot/cold lists remain stable. > This would not any of the problems you described as long as we hold > the lock for the hot/cold list during buld-volatile. I was not talking about free pages, and I don't think Rik was either. The idea is to be lazy about the make-volatile calls. Put the pages for which a make-volatile call should be done to some array/list and do a bulk make-volatile. These pages are still in the page/swap cache. The trouble is we have to be sure these pages have not been freed in the meantime. The bulk set-unused/set-stable to the buddy allocator should not be to problematic. We just have to find new places where to do the calls. -- blue skies, Martin. Martin Schwidefsky Linux for zSeries Development & Services IBM Deutschland Entwicklung GmbH "Reality continues to ruin my life." - Calvin.
