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Matthew Ahrens
4e1d1b4b92
If the system is very low on memory (specifically, `arc_free_memory() < arc_sys_free/2`, i.e. less than 1/16th of RAM free), `arc_evict_state_impl()` will defer wakups. In this case, the arc_evict_waiter_t's remain on the list, even though `arc_evict_count` has been incremented past their `aew_count`. The problem is that `arc_wait_for_eviction()` assumes that if there are waiters on the list, the count they are waiting for has not yet been reached. However, the deferred wakeups may violate this, causing `ASSERT(last->aew_count > arc_evict_count)` to fail. This commit resolves the issue by having new waiters use the greater of `arc_evict_count` and the last `aew_count`. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: George Amanakis <gamanakis@gmail.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11285 Closes #11397