[OpenSIPS-Users] Fine tuning high CPS and msyql queries

Alex Balashov abalashov at evaristesys.com
Sat Jun 13 00:23:18 EST 2020

On 6/12/20 8:03 PM, Calvin Ellison wrote:

> That's been the point of this discussion. Unfortunately, there answers 
> so far have added to up "keep changingĀ settings until you find what 
> works best" and "buffers are a Ponzi scheme" despiteĀ and immediate 3x 
> performance increase.

Perhaps if one adopts a rather esoteric understanding of "performance 
increase" ... in principle, queueing more packets indicates the 
opposite. In that light, one could look at a lower receive queue depth 
as an optimisation, actually.

One should see the forest for the trees, instead of cultivating a myopic 
preoccupation with short-term, stop-gap solutions.

Two things are logically possible:

(1) The receive queue backlog keeps stacking up until the size of 16.7m 
is exhausted as well; this is clearly not happening, or it would not be 
triumphantly claimed as a solution;

(2) The higher buffer provides the elasticity needed to cope with 
stochastic I/O wait conditions which, for a given base CPS load, occur 
within a certain range of latencies and at a certain frequency 
distribution. Because the blocking conditions are not always uniformly 
present--they're stochastic, after all--in those low-tide moments, the 
receive queue drains.

The larger buffer solves #2, but not by way of providing for a 
"performance increase". Nothing is performing better. It's a lever--a 
quite imperfect one--to cope with the fact that something is performing 
_quite poorly_. However, fortunately for you, it happens on an 
intermittent basis, otherwise you'd have quickly encountered scenario #1.

#2 is a better and more manageable problem than #1, in strictly relative 
terms, but both are pathological and need to be addressed. To say that 
this amounts to a "tuning" or "optimisation" that yields a "performance 
increase" is profoundly misleading.

-- Alex

Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

More information about the Users mailing list