On 01/23/2011 05:58 PM, David Rientjes wrote:

0e093d99763e (writeback: do not sleep on the congestion queue if there
are no congested BDIs or if significant congestion is not being
encountered in the current zone) uncovered a livelock in the page
allocator that resulted in tasks infinitely looping trying to find memory
and kswapd running at 100% cpu.

The issue occurs because drain_all_pages() is called immediately
following direct reclaim when no memory is freed and try_to_free_pages()
returns non-zero because all zones in the zonelist do not have their
all_unreclaimable flag set.

Reviewed-by: Rik van Riel <redacted>

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