NPTL in RH9 vs RHEL3

[Jakub Jelinek]

On Wed, Apr 14, 2004 at 06:38:37PM -0500, Harkrider, Larry wrote:
> I run SAPDB on Redhat9, and am trying to migrate to RHEL3.  It is well known
> that SAPDB requires the LD_ASSUME_KERNEL=2.2.5 to run on Redhat.  Using this
> settings, I have run SAPDB on Redhat9 with great success.  The same tactic
> on RHEL3 results in a much slower, and less stable database.
> 
> It seems that on Redhat9, the LD_ASSUME_KERNEL=2.2.5 disables floating
> stacks, but somehow leaves NPTL operational (as opposed to toggling
> linuxthreads).  The getconf command indicates this overtly:
> 
> [RH9]# getconf GNU_LIBPTHREAD_VERSION
> NPTL 0.29
> 
> On RHEL3, however, setting LD_ASSUME_KERNEL=2.2.5 results in nptl being
> disabled in favor of linuxthreads:
> 
> [RHEL3]# getconf GNU_LIBPTHREAD_VERSION
> linuxthreads-0.10

LD_ASSUME_KERNEL=2.2.5 env variable setting is exactly about forcing
non-FLOATING_STACKS linuxthreads.
On RHL9 I get:
rpm -q glibc; LD_ASSUME_KERNEL=2.2.5 getconf GNU_LIBPTHREAD_VERSION; getconf GNU_LIBPTHREAD_VERSION
glibc-2.3.2-27.9.6
linuxthreads-0.10
NPTL 0.34

and RHEL3:
rpm -q glibc; LD_ASSUME_KERNEL=2.2.5 getconf GNU_LIBPTHREAD_VERSION; getconf GNU_LIBPTHREAD_VERSION
glibc-2.3.2-95.20
linuxthreads-0.10
NPTL 0.60

There is no difference in this regard.  If NPTL is used on RHL9 with
LD_ASSUME_KERNEL=2.2.5, then something is broken with your setup, but
if that works for you, then you shouldn't actually use LD_ASSUME_KERNEL.

> I also see significant differences when running top on the machines.  On the
> RH9 box, the number of SAPDB processes remains minimal.  One the RHEL3 box,
> I see dozens of SAPDB processes.  Java behaves similarly.

NPTL threads share the same pid, while LinuxThreads uses one pid for each
thread.

	Jakub