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    SubjectRe: [PATCH 4/4] mm: vmscan: Only read new_classzone_idx from pgdat when reclaiming successfully
    Hi Mel,

    Too late review.
    At that time, I had no time to look into this patch.

    On Fri, Jun 24, 2011 at 03:44:57PM +0100, Mel Gorman wrote:
    > During allocator-intensive workloads, kswapd will be woken frequently
    > causing free memory to oscillate between the high and min watermark.
    > This is expected behaviour. Unfortunately, if the highest zone is
    > small, a problem occurs.
    > When balance_pgdat() returns, it may be at a lower classzone_idx than
    > it started because the highest zone was unreclaimable. Before checking


    > if it should go to sleep though, it checks pgdat->classzone_idx which
    > when there is no other activity will be MAX_NR_ZONES-1. It interprets


    > this as it has been woken up while reclaiming, skips scheduling and

    Hmm. I can't understand this part.
    If balance_pgdat returns lower classzone and there is no other activity,
    new_classzone_idx is always MAX_NR_ZONES - 1 so that classzone_idx would be less than
    new_classzone_idx. It means it doesn't skip scheduling.

    Do I miss something?

    Kinds regards,
    Minchan Kim

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