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    SubjectRE: [RFC][PATCH] avoid swapping out with swappiness==0
    Hi Rik,

    Thank you for reviewing.

    On 03/02/2012 05:47 PM, Rik van Riel wrote:
    > On 03/02/2012 12:36 PM, Satoru Moriya wrote:
    >> @@ -1999,7 +1999,7 @@ out:
    >> unsigned long scan;
    >>
    >> scan = zone_nr_lru_pages(mz, lru);
    >> - if (priority || noswap) {
    >> + if (priority || noswap || !vmscan_swappiness(mz, sc)) {
    >> scan>>= priority;
    >> if (!scan&& force_scan)
    >> scan = SWAP_CLUSTER_MAX;
    >
    > However, I do not understand why we fail to scale the number of pages
    > we want to scan with priority if "noswap".
    >
    > For that matter, surely if we do not want to swap out anonymous pages,
    > we WANT to go into this if branch, in order to make sure we set "scan"
    > to 0?
    >
    > scan = div64_u64(scan * fraction[file], denominator);
    >
    > With your patch and swappiness=0, or no swap space, it looks like we
    > do not zero out "scan" and may end up scanning anonymous pages.

    With my patch, if swappiness==0 or noswap==1, fraction[file] is
    set to 0. As a result, scan will be set to 0, too.

    > Am I overlooking something? Is this correct?
    >
    > I mean, it is Friday and my brain is very full...

    Have a nice weekend ;)

    Regards,
    Satoru
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