On Tue, Apr 28, 2015 at 3:54 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > I had a totally different implementation idea in mind. It goes > something like this: > > For each CPU, we allocate a fixed number of PCIDs, e.g. 0-7. We have > a per-cpu array of the mm [1] that owns each PCID. [...] We've done this before on other architectures. See for example alpha. Look up "__get_new_mm_context()" and friends. I think sparc does the same (and I think sparc copied a lot of it from the alpha implementation). Iirc, the alpha version just generates a (per-cpu) asid one at a time, and has a generation counter so that when you run out of ASID's you do a global TLB invalidate on that CPU and start from 0 again. Actually, I think the generation number is just the high bits of the asid counter (alpha calls them "asn", intel calls them "pcid", and I tend to prefer "asid", but it's all the same thing). Then each thread just has a per-thread ASID. We don't try to make that be per-thread and per-cpu, but instead just force a new allocation when a thread moves to another CPU. It's not obvious what alpha does, because we end up hiding the per-thread ASN in the "struct pcb_struct" (in 'struct thread_info') which is part the alpha pal-code interface. But it seemed to work and is fairly simple. I think something very similar should work with intel pcid's. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>