When a cache line is brought into the L1 cache,
another line must be evicted to make room for it. When lines in active use are
evicted, a performance problem may arise from continually rotating data back
into the cache. This metric measures the percentage of all replacements due to
each row. For example, if the grouping is set to 'Function', this metric shows
the percentage of all replacements due to each function, summing up to 100%.
This row is responsible for a majority of all L1 cache replacements.
Some replacements are unavoidable, and a high level of replacements may not
indicate a problem. Consider this metric only when looking for the source of a
significant number of L1 cache misses for a particular grouping. If these
replacements are marked as a problem, try rearranging data structures (for
example, moving infrequently-used data away from more-frequently-used data so
that unused data is not taking up cache space) or re-ordering operations (to
get as much use as possible out of data before it is evicted).