title: Knitr takes several minutes before processing the Rmd file
body: <p>I am using knitr to create html document but the compilation takes several minutes <strong>before</strong> processing the file and takes like 2 minutes after the process to show the output.
  <a href="https://i.stack.imgur.com/rmunp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rmunp.png" alt=""></a></p>
  
  <p>Nothing appears for minutes and then :</p>
  
  <p><a href="https://i.stack.imgur.com/Jh4Uh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Jh4Uh.png" alt="enter image description here"></a></p>
  
  <p>I have tried different computers and different YAML using the most basic :</p>
  
  <pre><code>---
  title: "Untitled"
  output: html_document
  ---
  </code></pre>
  
  <p>or </p>
  
  <pre><code>---
  title: "xxx"
  output: rmdformats::readthedown
  ---
  </code></pre>
  
  <p>I had issues with knitr and I found this solution :
  <a href="https://github.com/rstudio/rstudio/issues/4462" rel="nofollow noreferrer">https://github.com/rstudio/rstudio/issues/4462</a></p>
  
  <p>But now it takes forever to compile a document.</p>
  
  <p>I am using files on a local network (quite bad performances), I don't know if it can explain my issue.</p>
  
  <p>The code in chunks can be executed in less than 1 minute.</p>
  
  <p><strong>How to improve the compilation of .Rmd files ?</strong></p>