Timing HTTP Requests with cURL

Sometimes you just need to quickly benchmark how fast a page can be loaded (or fetched to be more precise). For these cases, cURL is a great option for timing HTTP requests.

$ curl -s -w "%{time_total}\n" -o /dev/null http://www.google.com/

Want a few more datapoints?? Thanks to ZSH, it’s easy to just loop around it:

$ for i in {1..3}; curl -s -w "%{time_total}\n" -o /dev/null http://www.google.com/

And if you’re a bash lover:

$ for i in {1..3};do curl -s -w "%{time_total}\n" -o /dev/null http://www.google.com/; done

Default behavior on cURL is GET, but you can do POST, DELETE, PUT and more complex requests. If you’re not familiar with cURL, best place to start is the manpage.

Besides “time_total”, curl also provides other timing, like “time_namelookup”, “time_connect”, etc. Checking a post by Joseph, I remembered that curl supports formatted output. This way we can create a “template” for our HTTP timing test:

Assuming the format file is named “curl-format”, we can execute a request:

$ curl -w "@curl-format" -o /dev/null -s http://www.google.com/
            time_namelookup:  0.416
               time_connect:  0.435
            time_appconnect:  0.000
           time_pretransfer:  0.435
              time_redirect:  0.000
         time_starttransfer:  0.488
                 time_total:  0.491


  • -w “@curl-format” tells cURL to use our format file
  • -o /dev/null redirects the output of the request to /dev/null
  • -s tells cURL not to show a progress bar
  • http://www.google.com/ is the URL we are requesting

The timings are DNS lookup, TCP connect, pre-transfer negotiations, start to end of transfer, redirects (in this case there were none), time to first byte, and total time (last byte), respectively.

Looking for something a bit more “complete”? You can always try Apache Benchmark:

$ ab -n 3 http://www.google.com/
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking www.google.com (be patient).....done
Server Software: gws
Server Hostname: www.google.com
Server Port: 80
Document Path: /
Document Length: 10928 bytes
Concurrency Level: 1
Time taken for tests: 0.231 seconds
Complete requests: 3
Failed requests: 2
(Connect: 0, Receive: 0, Length: 2, Exceptions: 0)
Write errors: 0
Total transferred: 35279 bytes
HTML transferred: 32984 bytes
Requests per second: 12.99 [#/sec] (mean)
Time per request: 76.999 [ms] (mean)
Time per request: 76.999 [ms] (mean, across all concurrent requests)
Transfer rate: 149.15 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 19 21 1.8 22 22
Processing: 50 56 5.3 59 61
Waiting: 46 51 4.0 53 53
Total: 73 77 5.0 79 82
Percentage of the requests served within a certain time (ms)
50% 76
66% 76
75% 82
80% 82
90% 82
95% 82
98% 82
99% 82
100% 82 (longest request)

Finding process memory usage on Linux

Recently I came up with a script to quickly print the memory utilization of specific processes on Linux. It’s very simple, but proven to be very handy while I was moving and tuning my VPSs. It quickly showed me that Apache was taking pretty much all my memory and motivated the migration to nginx.

It’s currently set to get the Resident Set Size (RSS), but you can easily change it to use Virtual Memory (VSZ). Just change ‘rss’ to ‘vsz’ in the ps commands. Also, you can add more processes to the script. Just add a new line and change the process name.