On Fri, Sep 05, 2014 at 10:14:16AM -0400, Theodore Ts'o wrote: > On Fri, Sep 05, 2014 at 04:32:48PM +0900, Joonsoo Kim wrote: > > I also test another approach, such as allocate freepage in CMA > > reserved region as late as possible, which is also similar to your > > suggestion and this doesn't works well. When reclaim is started, > > too many pages reclaim at once, because lru list has successive pages > > in CMA region and these doesn't help kswapd's reclaim. kswapd stop > > reclaiming when freepage count is recovered. But, CMA pages isn't > > counted for freepage for kswapd because they can't be usable for > > unmovable, reclaimable allocation. So kswap reclaim too many pages > > at once unnecessarilly. > > Have you considered putting the pages in a CMA region in a separate > zone? After all, that's what we originally did with brain-damaged > hardware that could only DMA into the low 16M of memory. We just > reserved a separate zone for that? That way, we could do > zone-directed reclaim and free pages in that zone, if that was what > was actually needed. Sorry for long delay. It was long holidays. No, I haven't consider it. It sounds good idea to place the pages in a CMA region into a separate zone. Perhaps we can remove one of migratetype, MIGRATE_CMA, with this way and it would be a good long-term architecture for CMA. I don't know exact history and reason why CMA is implemented in current form. Ccing some experts in this area. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
