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    SubjectRe: [PATCH 4/13] memcg: force_empty moving account
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    On Mon, 2008-09-22 at 20:00 +0900, KAMEZAWA Hiroyuki wrote:

    > + /* For avoiding race with speculative page cache handling. */
    > + if (!PageLRU(page) || !get_page_unless_zero(page)) {
    > + list_move(&pc->lru, list);
    > + spin_unlock_irqrestore(&mz->lru_lock, flags);
    > + yield();

    Gah, no way!

    > + spin_lock_irqsave(&mz->lru_lock, flags);
    > + continue;
    > + }
    > + if (!trylock_page(page)) {
    > + list_move(&pc->lru, list);
    > put_page(page);
    > - if (--count <= 0) {
    > - count = FORCE_UNCHARGE_BATCH;
    > - cond_resched();
    > - }
    > - } else
    > - cond_resched();
    > - spin_lock_irqsave(&mz->lru_lock, flags);
    > + spin_unlock_irqrestore(&mz->lru_lock, flags);
    > + yield();

    Seriously?!

    > + spin_lock_irqsave(&mz->lru_lock, flags);
    > + continue;
    > + }
    > + if (mem_cgroup_move_account(page, pc, mem, &init_mem_cgroup)) {
    > + /* some confliction */
    > + list_move(&pc->lru, list);
    > + unlock_page(page);
    > + put_page(page);
    > + spin_unlock_irqrestore(&mz->lru_lock, flags);
    > + yield();

    Inflicting pain..

    > + spin_lock_irqsave(&mz->lru_lock, flags);
    > + } else {
    > + unlock_page(page);
    > + put_page(page);
    > + }
    > + if (atomic_read(&mem->css.cgroup->count) > 0)
    > + break;
    > }
    > spin_unlock_irqrestore(&mz->lru_lock, flags);

    do _NOT_ use yield() ever! unless you know what you're doing, and
    probably not even then.

    NAK!



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