How slow is Go's reflection effectively?

[tomwilde]

In general we assume reflection is very slow, because for most languages this is painfully true.

But Go's reflection seems to be actually pretty lightweight. In my application I'm using the encoding/json package, as well as Gustavo Niemeyer's mgo MongoDB driver, both of which use reflection.

So, how bad does reflection impact a Go application's performance in general terms?

[Jesse McNelis]

'Slow' is relative to the problem being solved and the time-frame
given to solve it.
Reflection in Go is slow because it needs to do quite a few allocations.
Doing lots of allocations in a loop that is run many millions of times
would be slow if the loop needs to be complete in a few seconds. But
irrelevant if you have minutes.

Reflection can often lead to shorter and more reusable code which will
suit most people's needs until they profile their
solution and see if the reflection is actually going to be a
bottleneck. You won't know the impact of reflection on your
performance until you profile.


--
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http://jessta.id.au

[tomwilde]

Let me ask this in another way...

By using reflection in my DB queries and some other interaction that my web application server does - am I in the end reducing the amount of requests that the web server can serve per second or is the impact so small it won't even be noticeable?

I will do some profiling by using file-based data sources instead of databases.

Am Mittwoch, 18. Juli 2012 05:29:41 UTC+2 schrieb Jesse McNelis:

[David Symonds]

On Wed, Jul 18, 2012 at 1:32 PM, tomwilde <sedevel...@gmail.com> wrote:

> By using reflection in my DB queries and some other interaction that my web
> application server does - am I in the end reducing the amount of requests
> that the web server can serve per second or is the impact so small it won't
> even be noticeable?

For that situation, I would be very surprised to see reflection having
any measurable impact.


Dave.

[Dave Cheney]

Compared to a disk seek or network transfer, the cost of reflection will be negligible.