Latency Comparison Numbers.

latency.py

#!/usr/bin/env python

"""
Latency Comparison Numbers

If L1 access where a one second

based on number from https://gist.github.com/jboner/2841832
"""

CPU_CYCLE = 0.3 # level 1 cache access latency in nanos

lmap = {
"CPU cycle"                          :  CPU_CYCLE,
"L1 cache reference"                 :       0.5 ,
"Branch mispredict"                  :         5 ,
"L2 cache reference"                 :         7 ,
"Mutex lock/unlock"                  :        25 ,
"Main memory reference"              :       100 ,
"Compress 1K bytes with Zippy"       :      3000 ,
"Send 1K bytes over 1 Gbps network"  :     10000 ,
"Read 4K randomly from SSD"          :    150000 ,
"Read 1 MB sequentially from memory" :    250000 ,
"Round trip within same datacenter"  :    500000 ,
"Read 1 MB sequentially from SSD"    :   1000000 ,
"Disk seek"                          :  10000000 ,
"Read 1 MB sequentially from disk"   :  20000000 ,
"Send packet CA->Netherlands->CA"    : 150000000 ,
"NFS request timeout"                : 30000000000,
"LTO4 Tape seek/access time"         : 55000000000 ,

}

from datetime import timedelta

DAYS_IN_YEAR = 365

def toHumanString(t):
  if abs(t.days) >  DAYS_IN_YEAR :
    years = t.days / DAYS_IN_YEAR
    return "%d years, %s" % (years, str( t - timedelta(days=years*DAYS_IN_YEAR)) )
  else:
    return str(t)


for k, value in sorted(lmap.iteritems(), key=lambda (k,v): (v,k)):
  latency = timedelta(seconds=value/CPU_CYCLE)
  print "%-36s : %s" % (k, toHumanString(latency))