The test populates the cache, then invalidates it, then tries to push
huge (10x times the segment size) chunks into seastar memory hoping that
the invalid entries will be evicted. The exit condition on the last
stage is -- total memory of the region (sum of both -- used and free)
becomes less than the size of one chunk.
However, the condition is wrong, because cache usually contains a dummy
entry that's not necessarily on lru and on some test iteration it may
happen that
evictable size < chunk size < evictable size + dummy size
In this case test fails with bad_alloc being unable to evict the memory
from under the dummy.
fixes: #7959
tests: unit(row_cache_test), unit(the failing case with the triggering
seed from the issue + 200 times more with random seeds)
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Message-Id: <20210309134138.28099-1-xemul@scylladb.com>
(cherry picked from commit 096e452db9)
35804855f9