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    SubjectRe: [PATCH v2] mm: add free_hot_cold_page_list helper
    Hugh Dickins wrote:
    > On Tue, 1 Nov 2011, Konstantin Khlebnikov wrote:
    >> This patch adds helper free_hot_cold_page_list() to free list of 0-order pages.
    >> It frees pages directly from the list without temporary page-vector.
    >> It also calls trace_mm_pagevec_free() to simulate pagevec_free() behaviour.
    > Sorry for not speaking up sooner, but I do like this patch very much
    > (and I'm content with your trace compatibility choice - whatever).
    > Not so much in itself, but because it then allows a further patch
    > (mainly to mm/vmscan.c) to remove two levels of pagevec, reducing
    > its deepest stack by around 240 bytes.

    That's Great. Also I don't like pagevec-based free because we sometimes do
    extra lru lock-unlock on vector overflow.

    > I have that patch, but keep putting off sending it in, because I want
    > to show a reclaim stack overflow that it prevents, but the new avoidance
    > of writeback in direct reclaim makes that harder to demonstrate. Damn!
    > One question on your patch: where you have release_pages() doing
    >> + list_add_tail(&page->lru,&pages_to_free);
    > That seems reasonable, but given that __pagevec_free() proceeds by
    > while (--i>= 0) {
    > , starting from the far end of the pagevec (the most recently added
    > struct page, the most likely to be hot), wouldn't you reproduce
    > existing behaviour more accurately by a simple list_add()?
    > Or have I got that back to front? If so, a comment on the
    > list_add_tail() would help me to remember why - thanks.
    > Hugh

    Ok, this reasonable. Any way, the second its user: shrink_page_list() puts pages at the front.

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