How to Read a Varnish Histogram?

Solution 1:

So the x-axis is the time it takes for the request to come into varnish and get sent back to the client. The |'s are the cache hits and the #'s are the misses. So you should see all the |'s on the left since that is a faster time.

So the left most numbers are faster.. the right most are slower..

now the 1:2 n= number.. Its numbers for the vertical scale and sample size. I wouldn't worry much about those.

But from that output.. you have a pretty fast cache going on.

Solution 2:

• '|' is cache HIT
• '#' is cache MISS
• 'n:m' numbers in left top corner is vertical scale
• 'n = 123' is number of requests that are being displayed
• X-axis is logarithmic time between request request from kernel to Varnish and response from Varnish to kernel.

The X-axis works like this:

• 1e1 = 10 sec
• 1e0 = 1 sec
• 1e-1 = 0.1 secs or 100 ms (milliseconds)
• 1e-2 = 0.01 secs or 10 ms
• 1e-3 = 0.001 secs or 1 ms or 1000 µs (microseconds)
• 1e-4 = 0.0001 secs or 0.1 ms or 100 µs
• 1e-5 = 0.00001 secs or 0.01 ms or 10 µs
• 1e-6 = 0.000001 secs or 0.001 ms or 1 µs or 1000 ns (nanoseconds)

Whole article explaining 'varnishhist' very nicely can be found here: Varnishhist – What Does it Tell Us, and official doc here: Varnish request histogram.

Another useful command is 'varnishstat' - Varnish Cache statistics.