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
Received on Mon Apr 20 2009 - 13:08:48 MDT
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