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    Subject[2.4] heavy-load under swap space shortage

    swap_out() seems always trying scan even if there are no swap space available.
    This keeps CPU(s) busy with rare successful page-out and may cause lock
    contention in big smp system.

    entry = get_swap_page()
    /* find no swap page available */

    How about checking nr_swap_pages first and giving up if it's 0?
    Applying the patch below extremely reduced systime consumption by swap_out
    under swap space shortage.

    Systems without swap also suffer from the same problem.

    Any comments?

    Best regards.
    NOMURA, Jun'ichi <>

    --- linux-2.4.24/mm/vmscan.c
    +++ linux/mm/vmscan.c
    @@ -326,8 +326,11 @@ out_unlock:
    static int swap_out(zone_t * classzone)
    int counter, nr_pages = SWAP_CLUSTER_MAX;
    struct mm_struct *mm;
    + if (nr_swap_pages <= 0)
    + return 0;

    counter = mmlist_nr << 1;
    do {
    if (unlikely(current->need_resched)) {

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      Last update: 2005-03-22 14:00    [W:0.026 / U:3.664 seconds]
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