On 2012-11-04 20:21, Avi Kivity wrote: > On 11/04/2012 10:30 AM, Jan Kiszka wrote: >> From: Jan Kiszka <jan.kis...@siemens.com> >> >> Cirrus is triggering this, e.g. during Win2k boot: Changes only on >> disabled regions require no topology update when transaction depth drops >> to 0 again. > > 817dcc5368988b0 (pci: give each device its own address space) mad this > much worse by multiplying the number of address spaces. Each change is > now evaluated N+2 times, where N is the number of PCI devices. It also > causes a corresponding expansion in memory usage.
I know... But this regression predates your changes, is already visible right after 02e2b95fb4. > > I want to address this by caching AddressSpaceDispatch trees with the > key being the contents of the FlatView for that address space. This > will drop the number of distinct trees to 2-4 (3 if some devices have > PCI_COMMAND_MASTER disabled, 4 if the PCI address space is different > from the cpu memory address space) but will fail if we make each address > space different (for example filtering out the device's own BARs). > > If this change also improves cpu usage sufficiently, then it will be > better than your patch, which doesn't recognize changes in an enabled > region inside a disabled or hidden region. True, though the question is how common such scenarios are. This one (cirrus with win2k) is already special. > In other words, your patch > fits the problem at hand but isn't general. On the other hand my > approach doesn't eliminate render_memory_region(), just the exec.c stuff > and listener updates. So we need to understand where the slowness comes > from. I would just like to have some even intermediate solution for 1.3. We can still make it more perfect later on if required. Jan
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