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    SubjectRe: [RFC PATCH 00/17] virtual-bus
    Anthony Liguori wrote:
    >> I don't think we even need that to end this debate. I'm convinced we
    >> have a bug somewhere. Even disabling TX mitigation, I see a ping
    >> latency of around 300ns whereas it's only 50ns on the host. This
    >> defies logic so I'm now looking to isolate why that is.
    >
    > I'm down to 90us. Obviously, s/ns/us/g above. The exec.c changes
    > were the big winner... I hate qemu sometimes.
    >
    >

    What, this:

    > diff --git a/qemu/exec.c b/qemu/exec.c
    > index 67f3fa3..1331022 100644
    > --- a/qemu/exec.c
    > +++ b/qemu/exec.c
    > @@ -3268,6 +3268,10 @@ uint32_t ldl_phys(target_phys_addr_t addr)
    > unsigned long pd;
    > PhysPageDesc *p;
    >
    > +#if 1
    > + return ldl_p(phys_ram_base + addr);
    > +#endif
    > +
    > p = phys_page_find(addr >> TARGET_PAGE_BITS);
    > if (!p) {
    > pd = IO_MEM_UNASSIGNED;
    > @@ -3300,6 +3304,10 @@ uint64_t ldq_phys(target_phys_addr_t addr)
    > unsigned long pd;
    > PhysPageDesc *p;
    >
    > +#if 1
    > + return ldq_p(phys_ram_base + addr);
    > +#endif
    > +
    > p = phys_page_find(addr >> TARGET_PAGE_BITS);
    > if (!p) {
    > pd = IO_MEM_UNASSIGNED;

    The way I read it, it will run only run slowly once per page, then
    settle to a cache miss per page.

    Regardless, it makes a memslot model even more attractive.


    --
    error compiling committee.c: too many arguments to function



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