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    SubjectRe: [PATCH] 2/2 Prezeroing large blocks of pages during allocation
    On Mon, 28 Feb 2005, Dave Hansen wrote:

    > On Sun, 2005-02-27 at 13:43 +0000, Mel Gorman wrote:
    > > + /*
    > > + * If this is a request for a zero page and the page was
    > > + * not taken from the USERZERO pool, zero it all
    > > + */
    > > + if ((flags & __GFP_ZERO) && alloctype != ALLOC_USERZERO) {
    > > + int zero_order=order;
    > > +
    > > + /*
    > > + * This is important. We are about to zero a block
    > > + * which may be larger than we need so we have to
    > > + * determine do we zero just what we need or do
    > > + * we zero the whole block and put the pages in
    > > + * the zero page.
    > > + *
    > > + * We zero the whole block in the event we are taking
    > > + * from the KERNNORCLM pools and otherwise zero just
    > > + * what we need. The reason we do not always zero
    > > + * everything is because we do not want unreclaimable
    > > + * pages to leak into the USERRCLM and KERNRCLM
    > > + * pools
    > > + *
    > > + */
    > > + if (alloctype != ALLOC_USERRCLM &&
    > > + alloctype != ALLOC_KERNRCLM) {
    > > + area = zone->free_area_lists[ALLOC_USERZERO] +
    > > + current_order;
    > > + zero_order = current_order;
    > > + }
    > > +
    > > +
    > > + spin_unlock_irqrestore(&zone->lock, *irq_flags);
    > > + prep_zero_page(page, zero_order, flags);
    > > + inc_zeroblock_count(zone, zero_order, flags);
    > > + spin_lock_irqsave(&zone->lock, *irq_flags);
    > > +
    > > + }
    > > +
    > > return expand(zone, page, order, current_order, area);
    > > }
    > >
    >
    > I think it would make sense to put that in its own helper function.
    > When comments get that big, they often reduce readability. The only
    > outside variable that gets modified is "area", I think.
    >
    > So, a static inline:
    >
    > area = my_new_function_with_the_huge_comment(zone, ..., area);
    >

    Will make that change in the next version. It makes perfect sense.

    > BTW, what kernel does this apply against? Is linux-2.6.11-rc4-v18 the
    > same as bk18?
    >

    It applies on top of 2.6.11-rc4 with the latest version of the placement
    policy. Admittedly, the naming of the tree is not very obvious.

    --
    Mel Gorman
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