On Wed, Feb 13, 2013 at 10:46 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > At the moment, KVM/ARM is quite heavy handed when it comes to i-cache > invalidation, as it is flushed on each stage-2 mapping. > > An alternative is to mark each page as non-executable (courtesy of the > XN flag), and then to invalidate the i-cache when the CPU tries to > execute a page. > > We're basically trading off invalidation for faults. Performance wise, > the performance difference is very modest (I've seen a 0.2% > improvement over 10 runs of "hackbench 100 process 1000"). But the > important thing in my opinion is that it reduces the impact of the VM > on the whole system (fault handling only impact the VM while > invalidation is global). > > Code wise, this introduce a bit of restructuring in our stage-2 > manipulation code, making the code a bit cleaner (IMHO). Note that > these patches are against my arm64 branch, and won't apply on anything > else. > > As always, comments welcome. > Hey Marc, I'll give this a once-over. From my initial glance there are some issues with the stage2_get_pte stuff if you think about section mappings later on, and while I kind of see the background, I'm not sure it's as bad as it's made out to be. In any case, we really need to measure the impact of this on both a wider range of workloads inside the VM and on the host performance. -Christoffer _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
