On Mon, 20 Apr 2009, Amos Jeffries wrote: > Gavin McCullagh wrote: >> Obviously I don't mean physical disk location, I mean >> "if my cache were eg halved in size, how many hits would I lose?". > > Ah, in my experience that is gained from long term monitoring of the hit > rates and tweaking. > For example on the wiki cache we had a small outage with the disk and > flipped it over to RAM-only for a few weeks. The munin graphs showed a > ~20% reduction in byte-hit ratio and ~15% drop in request-hit ratio. On > just 2 req/sec. I guess that'll work alright, though it's a little inconvenient. >> That was my guess alright, so requeueing is O(1). I presume traversal is >> not necessary for a HIT though, which means the position in the removal >> queue may not be easy to determine. > > No thats hashed, and the HIST gets immediately cut out and pasted at the > start. So still around O(1) or similar for the list actions. Right. As always, many thanks for the explanations, Gavin
