• Sasha Levin's avatar
    KVM: Intelligent device lookup on I/O bus · 743eeb0b
    Sasha Levin authored
    Currently the method of dealing with an IO operation on a bus (PIO/MMIO)
    is to call the read or write callback for each device registered
    on the bus until we find a device which handles it.
    Since the number of devices on a bus can be significant due to ioeventfds
    and coalesced MMIO zones, this leads to a lot of overhead on each IO
    Instead of registering devices, we now register ranges which points to
    a device. Lookup is done using an efficient bsearch instead of a linear
    Performance test was conducted by comparing exit count per second with
    200 ioeventfds created on one byte and the guest is trying to access a
    different byte continuously (triggering usermode exits).
    Before the patch the guest has achieved 259k exits per second, after the
    patch the guest does 274k exits per second.
    Cc: Avi Kivity <avi@redhat.com>
    Cc: Marcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: default avatarSasha Levin <levinsasha928@gmail.com>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
eventfd.c 15.3 KB