Description of Problem:
There are serious kernel IO bottlenecks in the 2.4.x kernel
that are impacting performance for enterprise applications such 
as Oracle. The result is high system time,etc. for enterprise workloads
making the results unacceptable for tpc benchmarks,etc. 
The bottlenecks are 
a) Bounce buffer allocation for RAM <= 4GB. See kernel 
profile for a test configuration. 
b) __make_request -  due to the global io_request_lock contention

Version-Release number of selected component (if applicable):
Kernel : 2.4.x

How Reproducible:


Steps to Reproduce:
1. System (4-Proc, 4 GB, 4 megaraid controllers-PERC3/DC)
2. Boot with profile=2
3. Run testdevices program 
   The compressed tar attachment includes a Makefile,
   source file tio.c and the executable 'tio'.
   The parameters to 'tio' are the size of the read and
   the time in seconds. 'testdevices' is the driver for this.
   On line 11 in this driver script you could modify the
   size of the read (multiblock) and the time.
   Right now these are set to 512k and 5 minutes
   respectively.

   Usage:

  ./testdevices /dev raw1 raw2 raw3 raw4
   where raw1, raw2, raw3 & raw4 are raw partitions created on 4
   different volumes (controllers), i.e., one process/controller

  ./testdevices /dev raw1 raw1 raw1 raw1
             four processes/controller doing reads

4. While testdevices is running, use iostat and readprofile to 
   determine io and kernel issues.

Actual Results:
See attached kernel profiles.

Expected Results:


Additional Information:
Patches such as 
a) Jens Axboe bounce buffer patch seem to fix issue a) above
b) Experimental patches for the global io lock