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    SubjectRe: [PATCH 3/7] CART - an advanced page replacement policy

    Hi Peter,

    On Thu, Sep 29, 2005 at 08:08:48PM +0200, Peter Zijlstra wrote:
    > The flesh of the CART implementation. Again comments in the file should be
    > clear.

    Having per-zone "B1" target accounted at fault-time instead of a global target
    strikes me.

    The ARC algorithm adjusts the B1 target based on the fact that being-faulted-pages
    were removed from the same memory region where such pages will reside.

    The per-zone "B1" target as you implement it means that the B1 target accounting
    happens for the zone in which the page for the faulting data has been allocated,
    _not_ on the zone from which the data has been evicted. Seems quite unfair.

    So for example, if a page gets removed from the HighMem zone while in the
    B1 list, and the same data gets faulted in later on a page from the normal
    zone, Normal will have its "B1" target erroneously increased.

    A global inactive target scaled to the zone size would get rid of that problem.

    Another issue is testing: You had some very interesting numbers before,
    how are things now?

    > Signed-off-by: Peter Zijlstra <>
    > mm/cart.c | 631 +++++++++++++++++++++++++++++++++++++++++++++
    > 7 files changed, 682 insertions(+), 35 deletions(-)
    > Index: linux-2.6-git/mm/cart.c
    > ===================================================================
    > --- /dev/null
    > +++ linux-2.6-git/mm/cart.c
    > @@ -0,0 +1,639 @@


    > +#define cart_cT ((zone)->nr_active + (zone)->nr_inactive + (zone)->free_pages)
    > +#define cart_cB ((zone)->present_pages)
    > +
    > +#define T2B(x) (((x) * cart_cB) / cart_cT)
    > +#define B2T(x) (((x) * cart_cT) / cart_cB)
    > +
    > +#define size_T1 ((zone)->nr_active)
    > +#define size_T2 ((zone)->nr_inactive)
    > +
    > +#define list_T1 (&(zone)->active_list)
    > +#define list_T2 (&(zone)->inactive_list)
    > +
    > +#define cart_p ((zone)->nr_p)
    > +#define cart_q ((zone)->nr_q)
    > +
    > +#define size_B1 ((zone)->nr_evicted_active)
    > +#define size_B2 ((zone)->nr_evicted_inactive)
    > +
    > +#define nr_Ns ((zone)->nr_shortterm)
    > +#define nr_Nl (size_T1 + size_T2 - nr_Ns)

    These defines are not not easy to read inside the code which
    uses them, I personally think that "zone->nr_.." explicitly is
    much clearer.
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      Last update: 2005-09-30 20:48    [W:0.024 / U:27.172 seconds]
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