> Here's a hint: the cost of a cache miss is generally about a hundred times 

100 times seems quite optimistic %)

quoted text
> 
> No, zlib isn't perfect, and nope, inflate_fast() is no "memcpy()". And 
> yes, I'm sure a pure memcpy would be much faster. But I seriously suspect 
> that a lot of the cost is literally in bringing in the source data to the 
> CPU. Because we just mmap() the whole pack-file, the first access to the 
> data is going to see the cost of the cache misses.

I would have thought that zlib has a sequential access pattern that the
CPU prefetchers have a easy time with hiding latency.

BTW I always wonder why people reason about cache misses in oprofile
logs without actually using the cache miss counters.

-Andi

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