I may look into this in more detail later, but I ran a simple benchmark 
comparison on my modest AWS EC2 server (ApacheBench can behave poorly on 

1) I ran ApacheBench w/ 6 processes to fetch a simple "hello world" static 
html file using only nginx. I got roughly 650 requests per second.

2) I then ran ApacheBench w/ 6 processes against one of my Racket web apps 
using a monitoring endpoint that does a simple db query to determine the 
health of the server, so this went from nginx (acting as a load balancer 
and https handler) to the Racket processes via proxy_pass (only 2 running 
in parallel) which exercises my custom dispatching and a simple postgres 
query. No continuations and completely stateless. I got roughly 350 
requests per second.

At first glance, that doesn't appear to be that much overhead when 
comparing the two. In fact, I would've expected the very small static html 
request to be significantly more than double the req/sec of the Racket app 
db request.

I developed Rails apps for over a decade, and I know my Racket web apps are 
significantly faster in similar "database backed web apps" context.

I believe there is something wrong with those benchmarks at the moment.


On Monday, June 1, 2020 at 3:40:52 PM UTC-4, Sam Tobin-Hochstadt wrote:
> I'm skeptical both of the DB explanation and the multi-core 
> explanation. As you say, the difference between something like Django 
> and Racket is much too large to be explained by that. For example, on 
> the "plaintext" benchmark, Racket serves about 700 req/sec (I get 
> similar results on my machine). Many of the benchmarks in languages 
> like Python and Ruby do more than 1000x better, which means that even 
> if we had perfect speedup on 32 cores, we'd be nowhere close. 
> Additionally, the "plaintext" benchmark doesn't touch the DB at all. I 
> tried commenting out all of the DB code entirely, and it did not 
> change the results. 
> My guess is that the web server is just doing a lot of per-response 
> work that would need to be optimized. 
> Sam 
> On Mon, Jun 1, 2020 at 2:12 PM George Neuner <gneu...@comcast.net 
> <javascript:>> wrote: 
> > 
> > 
> > On 6/1/2020 1:40 PM, Bogdan Popa wrote: 
> > > I replied earlier today off of my Phone, but, for whatever reason 
> > > (caught in the moderation queue?), it's not showing up in this thread. 
> > > 
> > > Here's what it said: 
> > > 
> > >     The reason for poor performance relative to the other 
> > >     langs/frameworks is that there is currently no easy way to take 
> > >     advantage of multiple cores using the web framework so that's 
> being 
> > >     benchmarked is single-core performance. 
> > > 
> > >     This is mainly a problem for benchmarks such as this, but not 
> really 
> > >     an issue in the real world where you'd just run multiple processes 
> > >     with a load balancer in front. 
> > 
> > Single core [by itself] doesn't explain the enormous performance 
> > difference between Racket and Django. 
> > 
> > I haven't looked at the Django submission - Python's (in)comprehensions 
> > give me a headache.  But Python's DB pool is threaded, and Python's 
> > threads are core limited by the GIL in all the major implementations 
> > (excepting Jython). 
> > 
> > There are a few things Python can do faster than Racket, but the VAST 
> > difference in performance shown in the techempower tests isn't explained 
> > by them.  My suspicion is that the Racket application is making too many 
> > database connections and not relying enough on its open connection 
> > pool.  Hundreds of trivial requests can be served in the time it takes 
> > to spin up a new backend process. 
> > 
> > YMMV, 
> > George 
> > 
> > -- 
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