Re: questions on callstubs and "link-count" in index translator

Ravishankar N <ravishankar@xxxxxxxxxx> · Sat, 27 Apr 2019 11:50:01 +0530



    On 26/04/19 10:53 PM, Junsong Li wrote:

    
        Hello
            list,
        
           
          I have a couple of
              questions on index translator implementation.
        
        
              Why does gluster need callstub
                and a different worker queue (and thread) to process
                those call stubs? Is it just to lower the priority of
                fops of internal inodes?
          
        
    As far as I know, this is to move the processing to background and
    free up the server thread to process other requests.

    
              What’s the purpose of “link-count” in xdata? It’s being
              used only in index_fstat and index_lookup. I see sometimes
              the key is assigned 0/1 after callback, and sometimes AFR
              uses it to store flag GF_XATTROP_INDEX_COUNT. Is the code
              purposely reusing the key?
          
        
    A non-zero link count means there are entries that are pending
      heal. AFR requests this information in lookup and fstat fops and
      updates priv->need_heal in the fop-callbacks. It then uses that
      information to not nullify the inodes of the entries fetched
      during a readdirp call, improving readdirp performance. 

    
    https://review.gluster.org/#/c/glusterfs/+/12507/ is the patch
      that introduced it. 

    
    HTH,

    Ravi

    
          Thanks,
          Junsong
        
      
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