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    SubjectRe: [PATCH 1/2] mm,mlock: drain pagevecs asynchronously
    (1/4/12 5:05 PM), Andrew Morton wrote:
    > On Sun, 1 Jan 2012 02:30:24 -0500
    > wrote:
    >> Because lru_add_drain_all() spent much time.
    > Those LRU pagevecs are horrid things. They add high code and
    > conceptual complexity, they add pointless uniprocessor overhead and the
    > way in which they leave LRU pages floating around not on an LRU is
    > rather maddening.
    > So the best way to fix all of this as well as this problem we're
    > observing is, I hope, to completely remove them.
    > They've been in there for ~10 years and at the time they were quite
    > beneficial in reducing lru_lock contention, hold times, acquisition
    > frequency, etc.
    > The approach to take here is to prepare the patches which eliminate
    > lru_*_pvecs then identify the problems which occur as a result, via
    > code inspection and runtime testing. Then fix those up.
    > Many sites which take lru_lock are already batching the operation.
    > It's a matter of hunting down those sites which take the lock
    > once-per-page and, if they have high frequency, batch them up.
    > Converting readahead to batch the locking will be pretty simple
    > (read_pages(), mpage_readpages(), others). That will fix pagefaults
    > too.
    > rotate_reclaimable_page() can be batched by batching
    > end_page_writeback(): a bio contains many pages already.
    > deactivate_page() can be batched too - invalidate_mapping_pages() is
    > already working on large chunks of pages.
    > Those three cases are fairly simple - we just didn't try, because the
    > lru_*_pvecs were there to do the work for us.

    got it. so, let's wait hugh's "mm: take pagevecs off reclaim stack" next spin
    and make the patches on top of it.

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      Last update: 2012-01-05 00:35    [W:0.022 / U:44.388 seconds]
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