Re: [go-nuts] Simple worker pool in golnag

[Robert Engels]

I think that distinction is splitting hairs a bit in the case of Go - usually when you speak of concurrent you are talking about completely disparate processes (in the context of an OS). A typically Go server might be handling many types of client requests but it can easily be viewed as it is parallelizing the "all the clients work" - the Go program runs concurrently with other OS programs, but is parallelizing its own work.

-----Original Message-----
From: Jesper Louis Andersen
Sent: Dec 30, 2019 3:41 PM
To: Robert Engels
Cc: Brian Candler , golang-nuts
Subject: Re: [go-nuts] Simple worker pool in golnag

On Mon, Dec 30, 2019 at 10:14 PM Robert Engels <reng...@ix.netcom.com> wrote:

Here is a simple test that demonstrates the dynamics https://play.golang.org/p/6SZcxCEAfFp (cannot run in playground)

Notice that the call that uses an over allocated number of routines takes 5x longer wall time than the properly sized one - this is due to scheduling and contention on the underlying structures. So blindly creating go routines does not achieve optimum performance for many workloads (even when the number of OS threads is capped).

rengels@rengels:~/gotest$ go run main_bench.go 

2.261805812s

1.311269725s

6.341378965s

Yes, this is unsurprising since the problem in the program is parallel.

In a typical concurrent problem, most work is sitting and waiting for some event to happen and those events are usually measured in several milliseconds. For those problems, the switching cost is very low given the other benefits you gain. The key property there is rarely about speed, but about description of the problem to the machine.

Go definitely leans toward concurrent problems. If you want to target parallel problems, you have other options which are better, depending on factors of distribution, GPU availability, etc.

--

J.

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