[Haskell-beginners] Warp and Yesod benchmark puzzle

[Felipe Almeida Lessa]

[Forwarding to Yesod's mailing list as well.  I'll copy all of the
original text below for those who aren't on haskell-beginners.]

On Fri, Aug 31, 2012 at 11:24 AM, Lorenzo Bolla <lbolla at gmail.com> wrote:
> Hi all,
>
> This is a question specific to the Yesod framework, but simple enough
> (I hope) to be considered a beginner question...
>
> I am puzzled by the performance of these two very simple web-servers,
> one written in Warp and another written in Yesod:
>
> === YESOD ===
>
> {-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses,
> TemplateHaskell #-}
> import Yesod
>
> data HelloWorld = HelloWorld
>
> mkYesod "HelloWorld" [parseRoutes|
> / HomeR GET
> |]
>
> instance Yesod HelloWorld
>
> getHomeR :: Handler RepHtml
> getHomeR = defaultLayout [whamlet|$newline always
> Hello World!
> |]
>
> main :: IO ()
> -- main = warpDebug 3000 HelloWorld
> main = warp 3000 HelloWorld
>
> === WARP ===
>
> {-# LANGUAGE OverloadedStrings #-}
>
> import Network.Wai
> import Network.HTTP.Types
> import Network.Wai.Handler.Warp (run)
> import Data.ByteString.Lazy.Char8 ()
>
> app :: Application
> app _ = return $ responseLBS
>     status200
>     [("Content-Type", "text/html")]
>     "Hello, Warp!"
>
> main :: IO ()
> main = do
>     putStrLn "http://localhost:8080/"
>     run 8080 app
>
> ===
>
> I've tested both using httperf:
> $> httperf --hog --client=0/1 --server=localhost --port=3000 --uri=/
> --rate=1000 --send-buffer=4096 --recv-buffer=16384 --num-conns=100
> --num-calls=100 --burst-length=20
>
> and I got very different results:
>
> YESOD: Request rate: 4048.0 req/s (0.2 ms/req)
> WARP: Request rate: 33656.2 req/s (0.0 ms/req)
>
> Now, I understand that Yesod is expected to be slower than the "raw"
> Warp, but I wasn't expecting a 10x slowdown, especially for such a
> trivial Yesod app (no db, no auth, etc.).
>
> [
> Compilation command was: ghc -Wall -O2 --make yesod.hs
> $ yesod version
> yesod-core version:1.1.0
> ]
>
> What is going on?
>
> Thanks,
> L.

This is actually a rather tricky and interesting question =).

My knee-jerk reaction is "profile!".  Profiling will give you more
clues about where the time is being spent.

As Bryce said, you're using defaultLayout and Hamlet, which should
slow things down.  Also, you're implicitly using clientsession, you
may try setting makeSessionBackend [1] to 'const $ return Nothing' and
see what kind of performance you get.

Cheers!

[1] http://hackage.haskell.org/packages/archive/yesod-core/1.1.1.1/doc/html/Yesod-Core.html#v:makeSessionBackend

-- 
Felipe.