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Home -> Community -> Mailing Lists -> Oracle-L -> more 64 bit vs. 32 bit
Here is part of an email I was forwarded from an IBM rep making the argument
for 64 bit. Anyone know anything about the JFS2 filesystem? The parts of
the text below that applied to Oracle 64 bit were originally highlighted in
blue but this was lost in the forward. You will have to sift the things that
apply to running 64 bit Oracle on 64 bit AIX as opposed to the benefitis
that would still exist running 32 but Oracle on 64 bit AIX.
The following is taken from the AIX 5L Version 5.2 - Performance Managment Guide
64-bit Kernel
Beginning with AIX 5.1, the operating system provides a 64-bit kernel that
addresses bottlenecks which
could have limited throughput on 32-way systems. POWER4 systems are
optimized for the 64-bit kernel,
which is intended to increase scalability of RS/6000 IBM eServer pSeries
systems. It is optimized for
running 64-bit applications on POWER4 systems. The code base for the 64-bit
kernel is almost identical to
that for the 32-bit kernel. However, 64-bit code is built using a more
advanced compiler.
The 64-bit kernel also improves scalability by allowing you to use larger
sizes of physical memory. The
32-bit kernel is limited to 96 GB of physical memory.
64-bit Applications on 32-bit Kernel
The performance of 64-bit applications running on the 64-bit kernel on
POWER4-based systems should be
greater than, or equal to, the same application running on the same
hardware with the 32-bit kernel. The
64-bit kernel allows 64-bit applications to be supported without requiring
system call parameters to be
remapped or reshaped. The 64-bit kernel applications use a more advanced
compiler that is optimized
specifically for the POWER4 system.
32-bit Applications on 64-bit Kernel
In most instances, 32-bit applications can run on the 64-bit kernel without
performance degradation.
However, 32-bit applications on the 64-bit kernel will typically have
slightly lower performance than on the
32-bit call because of parameter reshaping. This performance degradation is
typically not greater than 5%.
For example, calling the fork() comand might result in significantly more
overhead.
64-bit Applications on 64-bit Kernel, Non-POWER4 Systems
The performance of 64-bit applications under the 64-bit kernel on
non-POWER4 systems may be lower
than that of the same applications on the same hardware under the 32-bit
kernel. The non-POWER4
systems are intended as a bridge to POWER4 systems and lack some of the
support that is needed for
optimal 64-bit kernel performance.
64-bit Kernel Extensions on Non-POWER4 Systems
The performance of 64-bit kernel extensions on POWER4 systems should be the
same or better than their
32-bit counterparts on the same hardware. However, performance of 64-bit
kernel extensions on
non-POWER4 machines may be lower than that of 32-bit kernel extensions on
the same hardware
because of the lack of optimization for 64-bit kernel performance on
non-POWER4 systems.
Enhanced Journaled File System (JFS2)
Enhanced JFS (also known as JFS2) provides better scalability than JFS.
Additionally JFS2 is the default
file system for the 64-bit kernel. (However our benchmark image has JFS for
the OS filesystems. If you
install from the CDs with a 64bit kernel option, it will create the OS
filesystems as JFS2)
You can choose to use either JFS, which is the recommended file system
for 32-bit environments, or Enhanced JFS, which is recommended for 64-bit
kernel. For more information
on Enhanced JFS, see Monitoring and Tuning File Systems.
12.1 AIX 5L 64-bit kernel overview
AIX 5L provides a new, scalable, 64-bit kernel that
Provides simplified data and I/O device sharing for multiple applicationss
on the same system
Provides more scalable kernel extensions and device drivers that make full
use of the kernel's system resources and capabilities
Allows for future hardware development that will provide even larger
single
image systems ideal for server consolidation or workload scalability
The following sections provide a general understanding of the new 64-bit kernel.
12.1.1 Why a 64-bit kernel is needed
There are a combination of factors that drive the requirement for a 64-bit
kernel.
The primary factor is the trend in system design towards massive amounts of
system resources, terabytes of memory, hundreds of processors, and
thousands
of I/O slots. A resulting factor is that customers see these massive single
systems as an opportunity for server consolidation, migrating all of the
workloads
that used to be across a number of individual servers onto a single massive
server. The kernel is responsible for managing the physical resources as
well as
the process workload, all of which are growing exponentially.
Similar to the need for a database program to move from a 32-bit
environment to
a 64-bit environment in order to take advantage of the vast address space
to
efficiently manage more data in memory, the kernel also needs to move from
the
constrained 32-bit environment to a 64-bit environment to efficiently
support and
manage the ever-expanding resources and workload. Some specific examples
include:
Increasing the size of Virtual Memory Manager (VMM) data structures in
order to support the larger memory configurations
The increased number and size of data structures in the global kernel
address space required to support the possibility of thousands of physical
and
logical devices and their device drivers
The ability to scale kernel data types to more easily support greater than
32-bit addressability in areas of 64-bit user address space, large files,
number
of inodes, device numbering, thread IDs, and so on
12.1.2 64-bit kernel considerations
There are some points for consideration for this new 64-bit kernel.
Both 32-bit and 64-bit kernels are available.
Only 64-bit CHRP-compliant PowerPC machines are supported for the 64-bit
kernel.
Only 64-bit kernel extensions are supported; this means that no existing
32-bit kernel extensions can be reused for the 64-bit kernel.
Kernel extensions and device drivers must be compiled in 64-bit mode to be
loaded into the 64-bit kernel.
The 32-bit and 64-bit application environments are available on all 64-bit
platforms.
12.1.3 External page table scaling for 64-bit kernel (5.2.0)
Prior to AIX 5L Version 5.2, the number of processes an application creates
using fork() is limited to the remaining space in a PTA segment. This was
also a
restriction to the segments ability to create more virtual pages in
expanding itself.
This limitation has been removed from the Version 5.2 64-bit kernel using a
dynamic allocation and creation of PTA segments at a tailend as opposed to
the
frontend.
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Post, Ethan
INET: Ethan.Post_at_ps.net
Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services ---------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Tue Oct 07 2003 - 13:49:31 CDT
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