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Time-Saving Method for Sustaining an SDLC Link Connection When Application Data is Not Following

IP.com Disclosure Number: IPCOM000100633D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Ault, MB: AUTHOR [+3]

Abstract

Performance is improved by eliminating the operating system overhead associated with the thread switch from the interrupt handler thread to the device driver thread, as well as the overhead associated with queuing and dequeuing frames.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Time-Saving Method for Sustaining an SDLC Link Connection When Application Data is Not Following

       Performance is improved by eliminating the operating
system overhead associated with the thread switch from the interrupt
handler thread to the device driver thread, as well as the overhead
associated with queuing and dequeuing frames.

      Disclosed is a technique for sustaining an idle SDLC link
connection within the IBM OS/2* Extended Edition product.
      An SLDC device driver performs SDLC protocol management for the
IBM OS/2 Extended Edition 1.0 product.  In order to perform this
timing-sensitive processing, a time-critical non-preemptable thread
executes within the SDLC device driver.  Ordinarily, this thread
sleeps on a RAM semaphore until a received SDLC frame is queued for
processing by the device driver's level 3 interrupt handler.  Once a
frame is queued, the interrupt handler issues a semclear against the
RAM semaphore informing the time-critical thread that there is work
to be performed.  The time-critical thread wakes up, removes the
frame from the interrupt handler's queue, interprets the frame,
decides what frame(s) should be transmitted, and programs the adapter
hardware to transmit.  Processor overhead is incurred by this thread
switch from the interrupt thread to the time critical device driver
thread as well as by the queuing, dequeuing, etc., of the received
frame.

      The SDLC device driver's level 3 interrupt handler was desi...