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Nick Piggin wrote: > Balbir Singh wrote: > >> This makes me wonder if it makes sense to split up the LRU into page >> cache LRU and mapped pages LRU. I see two benefits >> >> 1. Currently based on swappiness, we might walk an entire list >> searching for page cache pages or mapped pages. With these >> lists separated, it should get easier and faster to implement >> this scheme >> 2. There is another parallel thread on implementing page cache >> limits. If the lists split out, we need not scan the entire >> list to find page cache pages to evict them. >> >> Of course I might be missing something (some piece of history) > > I actually had patches to do "split active lists" a while back. > > They worked by lazily moving the page at reclaim-time, based on > whether or not it is mapped. This isn't too much worse than the > kernel's current idea of what a mapped page is. > > They actually got a noticable speedup of the swapping kbuild > workload, but at this stage there were some more basic > improvements needed, so the difference could be smaller today. > > The other nice thing about it was that it didn't have a hard > cutoff that the current reclaim_mapped toggle does -- you could > opt to scan the mapped list at a lower ratio than the unmapped > one. Of course, it also has some downsides too, and would > require retuning... > Thanks, I am motivated to experiment with the idea. I guess I need to (re)discover the downsides for myself :-) -- Balbir Singh Linux Technology Center IBM, ISTL - 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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