• Borislav Petkov's avatar
    x86, hotplug: Fix powersavings with offlined cores on AMD · 93789b32
    Borislav Petkov authored
    ea530692 made a CPU use monitor/mwait
    when offline. This is not the optimal choice for AMD wrt to powersavings
    and we'd prefer our cores to halt (i.e. enter C1) instead. For this, the
    same selection whether to use monitor/mwait has to be used as when we
    select the idle routine for the machine.
    
    With this patch, offlining cores 1-5 on a X6 machine allows core0 to
    boost again.
    
    [ hpa: putting this in urgent since it is a (power) regression fix ]
    Reported-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
    Cc: stable@kernel.org # 37.x
    Cc: H. Peter Anvin <hpa@linux.intel.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Len Brown <lenb@kernel.org>
    Cc: Venkatesh Pallipadi <venki@google.com>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.hl>
    Signed-off-by: default avatarBorislav Petkov <borislav.petkov@amd.com>
    LKML-Reference: <1295534572-10730-1-git-send-email-bp@amd64.org>
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    93789b32
smpboot.c 36.4 KB