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AnswerRe: As some may know i'm writing a dissertation... Pin
patbob9-Jan-15 5:19
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GeneralAPOD PinPopular
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QuestionBottleneck, Bottleneck, Who's got the Bottleneck? Pin
Michael Breeden8-Jan-15 2:17
Michael Breeden8-Jan-15 2:17 
Greetings Folks,

I think this is an unusual situation and I am concerned about a few parts, but especially the machine and environment they want me to use.

As a later, hopefully final note, the bottleneck is then the memory swapping at the L1 and L2 cache memory of the CPU, including the memory "Bridges". So CPU count does not matter. Mad | :mad:


The story is that the company I work for uses an in house application that is fairly CPU intensive, file IO intensive and database intensive. It currently runs on 11 machines. Note that the databases seem to keep up with all 11 machines.

OK, So they wanted me to write a multi-threaded version of the application that would run "on one machine".

Can do (can did), but I'm concerned about a problem with resource limitations on processing. It's a question of where is the bottleneck. It seems to have handled the database IO OK when 11 machines were running. I told them that ideally I'd like a 2 CPU Athelon (with 16 cores each) machine and a number of SSD drives. This is my reasoning.

With that many cores, I wouldn't run out of threads. (The code does limit how many jobs are started at any time). We'll assume that it has 64 Gig of RAM, so there shouldn't be a bottleneck there. Now it does a lot of file IO, but testing shows the delay is at the file read. Writes are so fast that I assume the OS (Windows by the way) is buffering to RAM and I don't see it writing to disk. That doesn't work with reads, so my stats show 1.5 seconds is common for say 5 files read.

So there are two questions. The first is that if I have all these cores, RAM, SSD drives, no database limit. Where is the bottleneck? Is it the bus and does anyone have any thoughts on it?

The second question... the one that matters. I don't get the machine I want. I get the machine they give me and worse yet, they want it to run on VM Ware. I don't think they understand the problem and I understand why. This is an unusual model. I am replacing current physical machines with a "virtual machine" with each thread I create to process a "job". I am making my own specialized version of VM Ware. They say they can continuously give me more cores if I need them... why I have detailed performance statistics going into a JSON message to a database. (By the way, I assume it will be Intel, so there will be fewer, but faster cores. I'd rather have more, slower cores.) My real question is (especially if my bottleneck is the bus), how much of a penalty do I pay for VM Ware? If it controls/channels data throughput on the bus, I could take a huge hit. I'd appreciate any thoughts on this, especially if you know how VM Ware is going to effect it. Thanks, Mike

*** *** *** *** ***
OK then. For the people saying Profile, then what do I want to profile? I'm fairly familiar with Perfmon, but I don't think it is going to help here, This is why... Please show me the error of my ways. Remember, I am recording the DateTime.Now.Ticks, before and after 9 processes (db and file IO) to a JSON message (which is tossed on a UDP message for another server to write to database), so I have some good information to start with.
"There are five major resource areas that can cause bottlenecks and affect server performance: physical disk, memory, process, CPU, and network."
1. I will see physical disk problems if my diagnostics show any sudden changes in a read operation statistics.
2. Memory - Yah, I have to check this one and I will scream at the hardware people if it happens, but they swear it won't.
3. Process - At startup I record the threads in use and the application throttles how many jobs are being processed at once, so I know how many threads are being used. It can be changed dynamically from the web page that monitors the application by writing to the database which the application periodically polls. Again, this is a good one to look at so I can wretch at the hardware people if I don't have enough cores.
4. CPU - Same issue.
5. Network - Same issue, though file read times over the network will be recorded and file write times seem to be limited by RAM since hey seem to be buffered... They are very fast.

Yes, the Perfmon will be helpful, but the original question still stands. If these are not the bottlenecks because of multiple cores, Mucho RAM and multiple SSD drives, what bottleneck do I hit and when. Is it the bus? Will VM Ware make it worse? ... Thanks much.

modified 12-Jan-15 10:51am.

AnswerProfile, Profile, Profile PinPopular
Dan Neely8-Jan-15 2:54
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AnswerRe: Bottleneck, Bottleneck, Who's got the Bottleneck? Pin
Duncan Edwards Jones8-Jan-15 2:55
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Michael Breeden12-Jan-15 4:49
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