Archive for November, 2009

14 Nov, 2009

RAM Speed

Posted by Bhavin Turakhia | (6) Comments

To test the speed of RAM, I got Ramki to run a small program that writes a set of bytes into memory a billion times and ran 4 instances of it on a dual proc quad core machine. Below are the results of running four instances of the program simultaneously.

Result

output.1:       User time (seconds): 545.99
output.1:       System time (seconds): 1.33
output.1:       Elapsed (wall clock) time (h:mm:ss or m:ss): 9:07.38
output.1:       Involuntary context switches: 820

output.2:       User time (seconds): 250.90
output.2:       System time (seconds): 1.18
output.2:       Elapsed (wall clock) time (h:mm:ss or m:ss): 4:12.12
output.2:       Involuntary context switches: 378

output.3:       User time (seconds): 250.30
output.3:       System time (seconds): 1.15
output.3:       Elapsed (wall clock) time (h:mm:ss or m:ss): 4:11.49
output.3:       Involuntary context switches: 373

output.4:       User time (seconds): 563.62
output.4:       System time (seconds): 1.31
output.4:       Elapsed (wall clock) time (h:mm:ss or m:ss): 9:25.00
output.4:       Involuntary context switches: 845

Observations

  • The write speed was between 0.25 seconds per million writes to 0.55 seconds
  • Output.2 and .3 took half the time as that of .1 or .4
  • Don’t have a specific theory on why 2 of the cores did better than the other two
  • No processor affinity was set, and the processes were being scheduled on random processors after every context switch.
  • Seemingly the processes were accessing RAM simultaneously. In my limited knowledge that could mean a few things – Multi-channel FSB (Dual) and additionally while oneprocess was computing stuff the other processes could access the FSB. The program was using lrand48 to generate a random number to write data to random locations so as to ensure that we do not rely too much on the L1/L2 cache

Some reading

Category : 0-cosmos | TechTalk

4 Nov, 2009

Obese Footers :)

Posted by Bhavin Turakhia | (7) Comments

Fat footers are no longer an emerging trend and have rapidly become a standard navigation paradigm. This short post contains a bunch of useful links I gathered while researching “fat footers” (try and say that 5 times in rapid succession :) ) -

Feed your footers away!!

Category : 0-cosmos | TechTalk