Active Block I/O Scheduling System (ABISS), version 1

Active Block I/O Scheduling System (ABISS), version 1

[Werner Almesberger]

The Active Block I/O Scheduling System (ABISS) is an extension of the
hard-disk storage subsystem of Linux, whose main purpose is to provide
a guaranteed reading and writing bit rate to applications.

http://abiss.sourceforge.net/abiss-1.tar.gz
md5sum ae832bcb94d5f8f29bfe4f4a737b2831
sha1sum b57722be9f35b54806b17b896e0cdf48d1e0f9d1

The kernel parts are still for 2.6.7. (Upgrade to 2.6.9 coming soon.)

The highlights since the last release:
 
 - added libabiss, a wrapper library that provides unistd/stdio-like
   functions, prefixed with "abiss_", to open and access files with
   ABISS.
 
 - priorities are now per task, not per file, which greatly simplifies
   things, and better aligns them with Jens' priority design.
 
 - when refilling a buffer, the scheduler also tries to refill the
   buffers of other files which are close to needing a refill. This
   reduces the number of seeks if there are a few relatively slow
   real-time readers competing with greedy best-effort readers.
 
 - the whole "access prediction" mechanism for writes is gone. All
   it did was to provide an estimate even Murphy would find too
   pessimistic, and it needed a lot of file system specific code to do
   this.

 - switched from the "unofficial" UML patch 2.6.7-01 to the "official"
   2.6.7-1

The detailed list of changes is below. For additional information,
please have a look at http://abiss.sourceforge.net/

- Werner

----------------------------------- CHANGES -----------------------------------

Version 1 (21-OCT-2004)
-----------------------

General:

- README: corrected Nick Piggin's name
- Makefile: added SHA1 sum

Tools:

- rdrt now measures the time to move the playout point separately, and sports
  two new options, -p and -a, to print this time over run time, or in a
  histogram
- rdrt now limits memory allocations (can be turned off with new option -x),
  and its CPU priority can be lowered to normal with new option -o

abissd:

- abissd/var.c:var_assignment: forgot that strncpy does not always
  NUL-terminate its strings

Kernel:

- switched from "unofficial" uml-patch-2.6.7-01 to "official" uml-patch-2.6.7-1
- removed per-file (really per-inode) priorities, because we already have
  per-task priorities
- fs/abiss/sched_lib.c:abiss_hp_raise: set "sched_priority" to 1 instead of
  (invalid) 0
- removed /sys/block/.../default_priority
- fs/abiss/sched_test.c: in an abiss_st_query message, msg.u.query.page_state
  can now be NULL to omit retrieving the potentially large page state array
- removed access prediction for allocations
- added reserved space to "struct abiss_sched_test_prm", to allow for future
  extensions without breaking binary compatibility
- sched_test.c now tries to refill buffers of different files at the same time,
  to avoid excessive seeking
- fs/abiss/elevator.c: added some tracing to hunt down a heisenbug

-- 
  _________________________________________________________________________
 / Werner Almesberger, Buenos Aires, Argentina     werner@almesberger.net /
/_http://www.almesberger.net/____________________________________________/