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    SubjectRe: [PATCH 4/8] Shrink zcache based on memlimit
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    Hi,

    On Fri, Jul 16, 2010 at 9:37 PM, Nitin Gupta <ngupta@vflare.org> wrote:
    > User can change (per-pool) memlimit using sysfs node:
    > /sys/kernel/mm/zcache/pool<id>/memlimit
    >
    > When memlimit is set to a value smaller than current
    > number of pages allocated for that pool, excess pages
    > are now freed immediately instead of waiting for get/
    > flush for these pages.
    >
    > Currently, victim page selection is essentially random.
    > Automatic cache resizing and better page replacement
    > policies will be implemented later.

    Okay. I know this isn't end. I just want to give a concern before you end up.
    I don't know how you implement reclaim policy.
    In current implementation, you use memlimit for determining when reclaim happen.
    But i think we also should follow global reclaim policy of VM.
    I means although memlimit doen't meet, we should reclaim zcache if
    system has a trouble to reclaim memory.
    AFAIK, cleancache doesn't give any hint for that. so we should
    implement it in zcache itself.
    At first glance, we can use shrink_slab or oom_notifier. But both
    doesn't give any information of zone although global reclaim do it by
    per-zone.
    AFAIK, Nick try to implement zone-aware shrink slab. Also if we need
    it, we can change oom_notifier with zone-aware oom_notifier. Now it
    seems anyone doesn't use oom_notifier so I am not sure it's useful.

    It's just my opinion.
    Thanks for effort for good feature. Nitin.
    --
    Kind regards,
    Minchan Kim


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