Latency catalog & back of the guestimation.

Time ($ns$): Represents time measured in nanoseconds ($ns$).

Time ($μs$): Represents time measured in microseconds ($μs$).

Note: Every system under study should have it’s latency profile.

QA:

Latency Catalog

…

Category Operation Time (ns) Time (μs) Equivalent Human Time*
L1 cache reference 0.5 ns 0.0005 μs 0.5 sec
L2 cache reference 7 ns 0.007 μs 7 sec
L3 cache reference 20 ns 0.02 μs 20 sec
Main memory access (RAM) 100 ns 0.1 μs 1 min 40 sec
Compress 1KB with Zippy 3,000 ns 3 μs 1.4 hours
Send 1 KB over 1 Gbps network 10,000 ns 10 μs 4.6 hours
Read from SSD 150,000 ns 150 μs 1.7 days
Read from HDD 10,000,000 ns 10 ms 1 year
Send packet CA → Netherlands 150,000,000 ns 150 ms 15 years
Context Switch 1,000,000 ns 1 ms 1 week
Process creation 20,000,000 ns 20 ms 3 months
Disk I/O operation 100,000,000 ns 100 ms 10 years
TCP handshake 150,000,000 ns 150 ms 15 years
Select (syscall) 2,000,000 ns 2 ms 2 months
Cache miss (L1 → L2) 20 ns 0.02 μs 20 sec
Pipeline stall (1 cycle) 0.5 ns 0.0005 μs 0.5 sec
Data Systems Database query execution (simple) 100,000 ns 100 μs 1.7 days
Database query execution (complex) 1,000,000 ns 1 ms 1 week
Disk seek time (HDD) 5,000,000 ns 5 ms 2 hours
Browsers DOM manipulation (basic) 20,000 ns 20 μs 2.3 minutes
CSS rendering 100,000 ns 100 μs 1.7 days
JavaScript execution (single line) 50,000 ns 50 μs 12 minutes
HTTP request round trip (local network) 200,000 ns 200 μs 2.3 days
Java Object creation 20,000 ns 20 μs 2.3 minutes
Method call (local) 50,000 ns 50 μs 12 minutes
Garbage collection (minor) 500,000 ns 500 μs 1.4 hours
Garbage collection (major) 10,000,000 ns 10 ms 1 year
C++ Function call (local) 50,000 ns 50 μs 12 minutes
New object allocation (heap) 100,000 ns 100 μs 1.7 days
Virtual function call 200,000 ns 200 μs 2.3 days
Copy constructor (simple object) 200,000 ns 200 μs 2.3 days
C Function call (local) 20,000 ns 20 μs 2.3 minutes
Malloc allocation 50,000 ns 50 μs 12 minutes
Pointer dereferencing 10 ns 0.01 μs 1.2 seconds
Stack allocation 10,000 ns 10 μs 4.6 hours
Process Management Thread creation (empty) 1,000,000 ns 1 ms 1 week
Thread destruction 1,000,000 ns 1 ms 1 week
Thread context switch (local) 10,000,000 ns 10 ms 1 year
Thread context switch (remote) 50,000,000 ns 50 ms 5.7 days
Thread synchronization (mutex lock acquire) 100,000,000 ns 100 ms 10 years
Thread synchronization (mutex lock release) 50,000,000 ns 50 ms 5.7 days
Thread synchronization (condition variable wait) 200,000,000 ns 200 ms 2.3 years
Thread synchronization (semaphore wait) 50,000,000 ns 50 ms 5.7 days
Atomic Operations Atomic compare-and-swap (CAS) 50,000 ns 50 μs 12 minutes
Atomic fetch-and-add 100,000 ns 100 μs 1.7 days
Atomic increment 10,000 ns 10 μs 4.6 hours
Interrupt Handling Interrupt latency (CPU reaction time) 1,000 ns 1 μs 1.4 minutes
Interrupt handling overhead 10,000 ns 10 μs 4.6 hours
Interrupt vector table lookup 500 ns 0.5 μs 0.7 seconds
Interrupt context switch 2,000,000 ns 2 ms 2 months
Interrupt service routine execution 50,000 ns 50 μs 12 minutes
I/O Operations Disk read (HDD) 10,000,000 ns 10 ms 1 year
Disk write (HDD) 20,000,000 ns 20 ms 3 months
Network packet receive (100 Mbps) 100,000 ns 100 μs 1.7 days
Network packet send (100 Mbps) 100,000 ns 100 μs 1.7 days
File System File system metadata access (seek time) 50,000 ns 50 μs 12 minutes
File read operation (small) 150,000 ns 150 μs 1.7 days
File write operation (small) 200,000 ns 200 μs 2.3 days
File system mount 1,000,000 ns 1 ms 1 week
Memory Management Page fault (minor) 200,000 ns 200 μs 2.3 days
Page fault (major) 10,000,000 ns 10 ms 1 year
Memory allocation (malloc) 50,000 ns 50 μs 12 minutes
Memory deallocation (free) 10,000 ns 10 μs 4.6 hours
Memory paging swap in 1,000,000 ns 1 ms 1 week
Memory paging swap out 1,500,000 ns 1.5 ms 1.4 weeks
Scheduler Process scheduling (preemptive) 10,000,000 ns 10 ms 1 year
Process scheduling (non-preemptive) 1,000,000 ns 1 ms 1 week
Time slice expiration 100,000 ns 100 μs 1.7 days

References