[bind10-dev] initial memo on recursive server performance research

[JINMEI Tatuya / 神明達哉]

At Thu, 5 Jul 2012 09:47:58 +0800,
"Likun Zhang" <zlkzhy at gmail.com> wrote:

> > Would it be possible to do the analysis for the actual cache hit rate
> > rather than just the name appearing? Many of the popular web sites use
> > short ttls (30-300s) for the main target. which reduces the
> > effectiveness of caching.
> 
> Pre-fetch may helps here. the entries in cache will be refetched before they expire, in the last 10s, etc. but if the ttl is too short(less than 10s? we can give a min-ttl to stop it, :) ), it doesn't work.

Actually, I suspect it's one of the latency vs throughput tradeoff
issues.  prefetch could improve worst case latency, but it doesn't
(at least directly) help improve throughput.  In fact, it could worsen
overall throughput due to the more frequent attempt of external
transactions (which are expensive themselves).

I still think prefetch is a promising approach as latency is probably
important for popular queries, too, but we need to carefully assess
its pros and cons.

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.