• Dou Liyang's avatar
    irq/matrix: Spread managed interrupts on allocation · 76f99ae5
    Dou Liyang authored
    Linux spreads out the non managed interrupt across the possible target CPUs
    to avoid vector space exhaustion.
    
    Managed interrupts are treated differently, as for them the vectors are
    reserved (with guarantee) when the interrupt descriptors are initialized.
    
    When the interrupt is requested a real vector is assigned. The assignment
    logic uses the first CPU in the affinity mask for assignment. If the
    interrupt has more than one CPU in the affinity mask, which happens when a
    multi queue device has less queues than CPUs, then doing the same search as
    for non managed interrupts makes sense as it puts the interrupt on the
    least interrupt plagued CPU. For single CPU affine vectors that's obviously
    a NOOP.
    
    Restructre the matrix allocation code so it does the 'best CPU' search, add
    the sanity check for an empty affinity mask and adapt the call site in the
    x86 vector management code.
    
    [ tglx: Added the empty mask check to the core and improved change log ]
    Signed-off-by: default avatarDou Liyang <douly.fnst@cn.fujitsu.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: hpa@zytor.com
    Link: https://lkml.kernel.org/r/20180908175838.14450-2-dou_liyang@163.com
    76f99ae5
irq.h 38.6 KB