c-taylor opened a new issue #7504:
URL: https://github.com/apache/trafficserver/issues/7504


   Feature request.
   
   The parameter proxy.config.http.default_buffer_water_mark can be used to 
increase memory buffering when reading out of the cache. This can have really 
positive properties with high levels of concurrency when using read while 
writer, but at the expense of memory. On a busy system with high concurrency, 
increasing this value even slightly can consume large amounts of memory, and it 
is impossible to assert how much of that is 'useful'.
   'Useful' here is described as over buffering to both complete the write of 
the object, and to ensure the shared cursor is not dependent on the transfer 
rate of the first requester.
   
   The positive effects are at their greatest when:
   * Response size < default_buffer_water_mark
   * Read while writer enabled
   * High request concurrency
   
   RAM cost for little to no benefit:
   * Response size > buffer_water_mark
   
   ----
   
   The suggestion here is to add a new parameter:
     proxy.config.http.high_buffer_water_mark
   
   We should defer increasing the buffer_water_mark above default , and ONLY if:
   `default_buffer_water_mark < "Content Length" < high_buffer_water_mark`
   
   This should have the desired improvement for all responses within the RAM 
buffering threshold we set, and not incur the cost for larger files outside of 
that window.


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