• Long Li's avatar
    genirq/affinity: Spread IRQs to all available NUMA nodes · 6dd7618d
    Long Li authored
    [ Upstream commit b8259219 ]
    
    If the number of NUMA nodes exceeds the number of MSI/MSI-X interrupts
    which are allocated for a device, the interrupt affinity spreading code
    fails to spread them across all nodes.
    
    The reason is, that the spreading code starts from node 0 and continues up
    to the number of interrupts requested for allocation. This leaves the nodes
    past the last interrupt unused.
    
    This results in interrupt concentration on the first nodes which violates
    the assumption of the block layer that all nodes are covered evenly. As a
    consequence the NUMA nodes above the number of interrupts are all assigned
    to hardware queue 0 and therefore NUMA node 0, which results in bad
    performance and has CPU hotplug implications, because queue 0 gets shut
    down when the last CPU of node 0 is offlined.
    
    Go over all NUMA nodes and assign them round-robin to all requested
    interrupts to solve this.
    
    [ tglx: Massaged changelog ]
    Signed-off-by: 's avatarLong Li <longli@microsoft.com>
    Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
    Reviewed-by: 's avatarMing Lei <ming.lei@redhat.com>
    Cc: Michael Kelley <mikelley@microsoft.com>
    Link: https://lkml.kernel.org/r/20181102180248.13583-1-longli@linuxonhyperv.comSigned-off-by: 's avatarSasha Levin <sashal@kernel.org>
    6dd7618d
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