• Vladimir Davydov's avatar
    mmu-notifier: add clear_young callback · 1d7715c6
    Vladimir Davydov authored
    In the scope of the idle memory tracking feature, which is introduced by
    the following patch, we need to clear the referenced/accessed bit not only
    in primary, but also in secondary ptes.  The latter is required in order
    to estimate wss of KVM VMs.  At the same time we want to avoid flushing
    tlb, because it is quite expensive and it won't really affect the final
    Currently, there is no function for clearing pte young bit that would meet
    our requirements, so this patch introduces one.  To achieve that we have
    to add a new mmu-notifier callback, clear_young, since there is no method
    for testing-and-clearing a secondary pte w/o flushing tlb.  The new method
    is not mandatory and currently only implemented by KVM.
    Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
    Reviewed-by: default avatarAndres Lagar-Cavilla <andreslc@google.com>
    Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Greg Thelen <gthelen@google.com>
    Cc: Michel Lespinasse <walken@google.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Pavel Emelyanov <xemul@parallels.com>
    Cc: Cyrill Gorcunov <gorcunov@openvz.org>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
mmu_notifier.c 11.7 KB