We are pleased to announce the 2.6.24.7-rt8 tree, which can be

downloaded from the location:
  http://rt.et.redhat.com/download/
Information on the RT patch can be found at:
  http://rt.wiki.kernel.org/index.php/Main_Page
Changes since 2.6.24.7-rt7
 - Read Write locks with multiple readers (Steven Rostedt)
 The previous versions of the RT tree would serialize the RW locks

 for all readers to allow for priority inheritance to take place.

 This change allows for multiple readers but still maintain priority

 inheritance. The number of readers that can hold a lock at any time

 may be limited by
   sysctl kernel.rwlocks_reader_limit
 Setting this to <= 0 will give allow for any number of readers. The

 default is set to NR_CPUS.
 ** Note: I made this change separate to allow for easy testing in case

          bugs have been introduced by this change.
to build a 2.6.24.7-rt8 tree, the following patches should be applied:
  http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.24.tar.bz2

  http://kernel.org/pub/linux/kernel/v2.6/patch-2.6.24.7.bz2

  http://rt.et.redhat.com/download/patch-2.6.24.7-rt8.bz2
And like always, my RT version of Matt Mackall's ketchup will get this

for you nicely:
  http://people.redhat.com/srostedt/rt/tools/ketchup-0.9.8-rt3
The broken out patches are also available.
-- Steve
--

Hi Steven,
I ran mysql+oltp (ro) on 2.6.24.7-rt7 and 2.6.25-rt2 to compare

throughput to their parent trees, and ended up with strange (and

verified) looking performance curves for both trees.  The changes in

2.6.24.7-rt8 and 2.6.25.4-rt3 cured the primary oddities.
(it looks to me like there may be a little load-balancing issue, peak

throughput isn't where it should be for my Q6600 box)
	-Mike
--

The difference between 24-rt7 and 24-rt8 as well as with 25-rt2 and 25-rt3

is the deserialization of rwlocks. The rt patch as always serialized

readers to allow for priority inheritance with rwlocks. I wrote a patch to

break that and allow for multiple readers and still keep the priority

inheritance.
Your test probably had a bottle neck on a rwlock (same for rwsems)

somewhere that the new code solved.
-- Steve

--

Ahem.  Attach the data _before_ poking xmit.