Messages in this thread | | | Date | Mon, 28 Jul 2008 17:28:59 -0700 | From | Jeremy Fitzhardinge <> | Subject | Comments on UV tlb flushing |
| |
I'm just reworking the x86 tlb code to use smp_call_function_mask, and I see how the UV tlb flushing hooks in. A few things occur to me:
1. There should be a CONFIG_X86_UV to select this code. tlb_uv.o is around 6k, which is not trivial overhead to subject every x86_64 kernel to. 2. CONFIG_X86_UV should either depend on or select CONFIG_PARAVIRT. 3. You should hook into paravirt_ops to enable your tlb-flush code. That is, in - say - uv_bau_init() you do "pv_mmu_ops.flush_tlb_others = uv_flush_tlb_others". This removes a test/branch in the generic code. Using paravirt_ops may open other opportunities to put UV-optimised functions in place without having to modify generic code.
My understanding is that the UV hardware has some kind of payload-carrying IPI mechanism, which is a capability could be useful to express in a higher-level way in the kernel. Certainly I could imagine using it in a virtual environment as a way to do inter-VCPU messaging with less context switch overhead.
Thanks, J
| |