In Sizing Details you may see an odd number like 40.27 cores for RAW cores as shown below
Actual Core Capacity
This is the total number of cores in the recommendation.
By clicking on the tooltip by the node you get the information
So in this recommendation we have 3 nodes where each has 2 cpu and each cpu has 8 cores. So the Actual core capacity is 3 nodes * 2 cpu/node * 8 cores/cpu = 48 cores
Applied Weight
Intel designs a wide range of cpus to meet different market needs. Core count certainly varies but the speed of a core is not the same across all cpu’s.
We need some benchmark to adjust for the core speed differences. We use SPECInt 2006. It is the best benchmark in terms of being an industry standard where vendors who publish numbers have to use standard testing process and publically publish the numbers. We see consistency as well for a given CPU across all the vendors. Thus this is a good benchmark to use for us to adjust for different values
So applied weight is where we have adjusted the cores to the baseline processor which runs at 42.31 specints
Review the Processor Table page with their core count, specints, and adjusted cores
Using this example we have a recommendation of 3 nodes with each node have quantity 2 2620v4 processors. The table (calculation is shown in that page too) shows the 2620 v4 adjusted cores is 14.9 cores with nodes having 2 cpus
Thus in this recommendation total effective cores is 14.91 cores/node * 3 nodes = 44.73 cores. We take applied weight adjustment of -3.26
Memory Adjustments
Broadwell Processors
With Broadwell processors “unbalanced DIMM” configuration depends on how they are laid out on the motherboard. When it occurs there is a 10% increased access latency
To determine whether Sizer takes a discount it takes total count of DIMMs in a node and divides by 4. If odd number then it is Unbalanced and Sizer applies the discount.
If even, then no reduction is needed
Example
12x32GB in a node. 12 DIMMs/4 = 3 and so unbalanced
8X32GB in a node 8 DIMMs/4 = 2 and so balanced
If unbalanced core capacity is reduced.
– Actual Core Capacity = Cores/Node * Node count
– Applied Wieght = extra or less cores vs baseline
– Adjustment due to Memory Issues = -10% * (RAW Cores+Applied Wieght)
It should be noted that if single processor system then NO adjustment is needed.
Skylake Processors
Skylake processors is more complex compared to Broadwell in terms of whether a system has unbalanced dimms
We now test for the following
- CPU – skylake
- Model – Balanced_Motherboard – true (described below)
- Memory bandwidth – go with slower figure for either memory or CPU. If 2133 Mhz then -10% memory adjustment. If 2400Mhz or 2666Mhz (most common with skylake models) we take a 0% adjustment
Like before, we find the DIMM count per socket. There is typically 2 sockets (cpu’s) but can be 1 and starting to introduce 4 socket models
Using the quantity of DIMMs per socket we should apply following rules
If CPU is skylake
- If dimm count per socket is 5,7,9,10,11 then the model is considered unbalanced and we need to take a -50% memory adjustment
- if dimm count per socket is 2,3,4, or 12 it is balanced and memory adjustment = 0%
- if model is balanced and DIMM count per socket is 6 or 8 then it is balanced and memory adjustment = 0%
- if model is unbalanced and DIMM count per socket is 6 or 8 then it is unbalanced and memory adjustment = -50%
After determining the adjustment percent we would make the adjustment as we do currently
- Actual core capacity = Total cores in the cluster
- Applied weight = adjustment vs baseline specint
- Adjustment = Adjustment Percent * (Actual core capacity – Applied weight)
With Skylake, it can matter how the DIMMs are arranged on the motherboard. We have PM review that and so far all models are laid out in balanced fashion
Here is doc that shows the options
