On Sun, 16 September 2007 11:44:09 -0700, Linus Torvalds wrote:
There may be another approach. We could create a never-pinned cache,
without trying hard to keep it full. Instead of moving a hot dentry at
dput() time, we move a cold one from the end of lru. And if the lru
list is short, we just chicken out.
Our definition of "short lru list" can either be based on a ratio of
pinned to unpinned dentries or on a metric of cache hits vs. cache
misses. I tend to dislike the cache hit metric, because updatedb would
cause tons of misses and result in the same mess we have right now.
With this double cache, we have a source of slabs to cheaply reap under
memory pressure, but still have a performance advantage (memcpy beats
disk io by orders of magnitude).
Jörn
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