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bitkeeper revision 1.1159.137.1 (41811b328SwfN4BTxZsoMM-iGa8evQ)

Delete some unused tools, lots of docs updates.
author mwilli2@equilibrium.research
date Thu Oct 28 16:15:46 2004 +0000 (2004-10-28)
parents 3ec9f0898ed8
children ad13896e776c
line source
1 Future plans and enhancements
2 =============================
4 For up-to-date details of features currently under implementation,
5 visit the Xen project roadmap at:
6 http://www.cl.cam.ac.uk/Research/SRG/netos/xen/roadmap.html
8 IO enhancements
9 ---------------
10 There are also a number of memory management enhancements that didn't
11 make this release: We have plans for a "universal buffer cache" that
12 enables otherwise unused system memory to be used by domains in a
13 read-only fashion.
15 Disk Scheduling
16 ---------------
17 The current disk scheduler is rather simplistic (batch round robin),
18 and could be replaced by e.g. Cello if we have QoS isolation
19 problems. For most things it seems to work OK, but there's currently
20 no service differentiation or weighting.
22 Improved load-balancing
23 -----------------------
24 Currently, although Xen runs on SMP and SMT (hyperthreaded) machines,
25 the scheduling is far from smart -- domains are currently statically
26 assigned to a CPU when they are created (in a round robin fashion).
27 We'd like to see a user-space load-balancing daemon that can shift
28 domains between CPUs as their activity changes.
30 Multiprocessor Guest VMs
31 ------------------------
32 Xen currently only supports uniprocessor guest OSes. We have designed
33 the Xen interface with MP guests in mind, and plan to build an MP
34 Linux guest in due course. Basically, an MP guest would consist of
35 multiple scheduling domains (one per CPU) sharing a single memory
36 protection domain. The only extra complexity for the Xen VM system is
37 ensuring that when a page transitions from holding a page table or
38 page directory to a write-able page, we must ensure that no other CPU
39 still has the page in its TLB to ensure memory system integrity. One
40 other issue for supporting MP guests is that we'll need some sort of
41 CPU gang scheduler, which will require some research.
43 Cluster Management
44 ------------------
45 There have been discussions regarding a unified cluster controller
46 for Xen deployments. This would leverage the existing features of
47 Xen to present a uniform control interface for managing a cluster
48 as a pool of resources, rather than a set of completely distinct
49 machines.
51 PAE Support on 32-bit x86
52 -------------------------
53 Xen can currently use up to 4GB of memory. It's possible for x86
54 machines to address more than that (64GB), but it requires using a
55 different page table format (3-level rather than 2-level) that we
56 currently don't support. Adding 3-level PAE support wouldn't be
57 difficult, but we'd also need to add support to all the guest
58 OSs. We do not plan to add this support ourselves but volunteers
59 are welcome!