On Sun, 25 Mar 2007 15:20:35 +0530 Balbir Singh <balbir@xxxxxxxxxx> wrote: > Andrew Morton wrote: > <snip> > > The problem is memory reclaim. A number of schemes which have been > > proposed require a per-container page reclaim mechanism - basically a > > separate scanner. > > > > This is a huge, huge, huge problem. The present scanner has been under > > development for over a decade and has had tremendous amounts of work and > > testing put into it. And it still has problems. But those problems will > > be gradually addressed. > > > > A per-container recaim scheme really really really wants to reuse all that > > stuff rather than creating a separate, parallel, new scanner which has the > > same robustness requirements, only has a decade less test and development > > done on it. And which permanently doubles our maintenance costs. > > > > The current per-container reclaim scheme does reuse a lot of code. As far > as code maintenance is concerned, I think it should be easy to merge > some of the common functionality by abstracting them out as different > functions. The container smartness comes in only in the > container_isolate_pages(). This is an easy to understand function. err, I think I'd forgotten about container_isolate_pages(). Yes, that addresses my main concern. > > So how do we reuse our existing scanner? With physical containers. One > > can envisage several schemes: > > > > a) slice the machine into 128 fake NUMA nodes, use each node as the > > basic block of memory allocation, manage the binding between these > > memory hunks and process groups with cpusets. > > > > This is what google are testing, and it works. > > Don't we break the global LRU with this scheme? Sure, but that's deliberate! (And we don't have a global LRU - the LRUs are per-zone). > > > > b) Create a new memory abstraction, call it the "software zone", which > > is mostly decoupled from the present "hardware zones". Most of the MM > > is reworked to use "software zones". The "software zones" are > > runtime-resizeable, and obtain their pages via some means from the > > hardware zones. A container uses a software zone. > > > > I think the problem would be figuring out where to allocate memory from? > What happens if a software zone spans across many hardware zones? Yes, that would be the tricky part. But we generally don't care what physical zone user pages come from, apart from NUMA optimisation. > The reclaim mechanism proposed *does not impact the non-container users*. Yup. Let's keep plugging away with Pavel's approach, see where it gets us. _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
