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Moore’s Law

Oracle Tips by Burleson Consulting

Moore’s Law

Back in the mid-1960’s, Gordon Moore, the director of the research and development labs at Fairchild Semiconductor, published a research paper titled “Cramming More Components into Integrated Circuits.”  In his paper, Moore performed a linear regression on the rate of change in server processing speed and costs and noted an exponential growth in processing power and an exponential reduction of processing costs.  This landmark paper gave birth to “Moore’s Law,” which postulated that CPU power will get four times faster every three years as illustrated in Figure 12.1.

 

Figure 12.1:  Moore’s Law for CPU speed

 

In the 1970’s, a 4-way Symmetric Multiprocessing (SMP) processor cost over three million dollars.  Yet today, the same CPU can be purchased for less than three thousand dollars.  CPUs will increase in speed four times every three years and only increase in cost by 50%.

 

While Moore’s Law is generally correct, the curve is not linear.  The formerly marginal rate of advances in CPU speed has increased dramatically in the past decade, most notably with the introduction of the Itanium2 processors.

 

The large RAM data buffers enabled by 64-bit operating systems have shifted the bottleneck for many Oracle databases from I/O to CPU.  Oracle10g accommodates this shift to CPU consumption by providing a new cpu_cost feature that allows Oracle’s cost-based SQL optimizer to evaluate SQL execution plan costs based on predicted CPU costs as well as I/O costs.  This is an adjustable feature in Oracle10g, and it is controlled by the _optimizer_cost_model  hidden parameter.

 

Even though it is true that a CPU bottleneck exists when the run queue exceeds the number of processors on the server, this condition does not always mean that the best solution is to add processors.  Excessive CPU load can be caused by many internal Oracle conditions including inefficient SQL statements that perform excessive logical I/O, non-reentrant SQL inside the library cache, and many other conditions.  Fortunately, Oracle 10g Enterprise Manager allows users to look back in time and find these conditions, even though the immediate run queue issue has passed.

 

While Moore’s law is quite correct for processor speed and cost, many have over-generalized this principle as it applies to disks and RAM.  It is true that costs are continually falling for RAM and disk, but the speed assumptions do not apply.


 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

Figure 12.2:  Moore’s Law for Disk speed

 

The old-fashioned spinning platters of magnetic-coated metal disks have an upper limit of spin speed, and the read/write head movement speed is limited.  In the early 1990’s, it became apparent that the 1950’s disk technology had reached the limits of its physical capabilities, and it became necessary for disk manufacturers to add on-board RAM caches to disk arrays and include asynchronous writing mechanisms to continue to improve disk speed.

 

One glaring exception to Moore’s law is RAM speed as shown in Figure 12.3 below. 

 

Figure 12.3:  Moore’s Law for RAM speed

 

RAM has not made many significant gains in speed since the mid 1970’s.  This is due to the limitations of silicon and the fact that access speed in nanoseconds approaches the speed of light.  The only way to further improve the speed of RAM would be to employ a radical new medium such as Gallium Arsenide.

 

This flat speed curve for RAM has important ramifications for Oracle processing.  Since CPU speed continues to outpace RAM speed, RAM sub-systems must be localized to keep the CPUs running at full capacity.  This type of approach is evident in the new Itanium2 servers where the RAM is placed as close to the CPU as possible as shown in Figure 12.4.

 

Figure 12.4:  Localizing RAM in Itanium2 Servers

 

This represents the Oracle servers of the 21st century (e.g. the UNISYS ES7000 series) which have a special L2 RAM that is placed near the processors for fast RAM access. As we have seen, low-cost RAM technology has dramatically changed the way that Oracle databases are tuned.

 

SEE CODE DEPOT FOR FULL SCRIPTS


This is an excerpt from my latest book "Oracle Tuning: The Definitive Reference". 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts:

http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm

 


 

 

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