Intel Xeon 3.6 2MB vs AMD Opteron 252 Database Test
by Jason Clark & Ross Whitehead on February 14, 2005 8:00 AM EST- Posted in
- IT Computing
SQL Stress Results
The SQL Stress results have changed somewhat from some of our earlier articles using this tool. We did a revamp of the tool itself, which is more performant on high volume queries. Also, we lengthened the test time to 20 minutes and changed the queries around some to reflect our current FuseTalk version. The new 2MB L2 Xeon part did quite well here, churning out a 7% gain over its 1MB counterpart. The Opteron 252 gained its usual 7% for its clock increase of 200MHz. There was no gain from the 1GHz HT link support as we discussed in our Test Hardware configuration on Page 2. Overall, the new Xeon 2MB part was the "hands down" winner for this test with a 13% lead over the Opteron 252, thanks to its 1MB cache boost.
Total queries executed
The number of queries that were executed throughout the duration of the test.
Queries per second
An average of how many queries per second were executed throughout the duration of the test.
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Viditor - Monday, February 14, 2005 - link
"DMA operations initiated by a peripheral device that does not directly support 64-bit addressing will have performance issues"I'm not sure you are correct in this...I believe the issue is
"physical addresses above 4GB (32 bits) cannot reliably be the source or destination of DMA operations"
I found another article that explains my concern quite well...
http://www.spodesabode.com/content/article/nocona/...
"Unlike the Itanium, which is solely a 64-Bit processor, these chips have the ability to run in both 32-Bit and 64-Bit mode. Some devices, such as a large majority of PCI cards cannot directly access memory above the 4GB point. To solve this, the software has to ensure the physical memory address is below the 4GB point. AMD solved this solution by using a hardware IOMMU, which is effectively a "bounce buffer" or look-up table of physically memory addresses corresponding to a virtual address that is given to the incompatible hardware, allowing it to use memory above the 4GB barrier.
Intels solution isn't quite as elegant. If a device needs to access memory above the 4GB point, the data is just copied from wherever it is, to a fixed location below the 4GB point. This takes time and can reduce performance. In extreme cases we have heard there could be as much as 30-50% decrease in performance on the Nocona platform"
This does not appear to be a 64bit driver issue to me as no mention in any of the access scenarios is described as 32bit...
Accord99 - Monday, February 14, 2005 - link
It's an Intel thing I think, for why they don't have an IOMMU. Even their chipsets for the Itanium 2 don't have one while HP and SGI's chipsets do. Or perhaps Intel just wants (and has the power to force) peripheral manufacturer's to make proper 64-bit devices and drivers.Viditor - Monday, February 14, 2005 - link
OIC what you are saying...and yes, it's a problem with the chipset. Of course that is exactly what I said in the first place..."Because there is still no hardware IOMMU on Xeon chipsets"
The big question is, why hasn't Intel fixed this?
I can only assume that it is a design problem for them that is inherent to EM64T...
I can't imagine that they would just let this slide on their chipset development.
What that problem is, I have no idea...I would just like to see what effect it has on system function.
Accord99 - Monday, February 14, 2005 - link
The linuxhardware article supports what I'm saying, DMA operations initiated by a peripheral device that does not directly support 64-bit addressing will have performance issues. Server-level peripherals typically support 64-bit addressing and it is not a problem with the CPU, or the EMT64 instruction set, it is a problem with the chipset. It does not affect the Xeon's ability to addres flatly >4GB of memory.Viditor - Monday, February 14, 2005 - link
I don't believe I do...I have read that post before, and I don't see your point.
Try reading this article to understand what I'm saying:
http://www.linuxhardware.org/article.pl?sid=04/10/...
“Software IOTLB — Intel EM64T does not support an IOMMU in hardware while AMD64 processors do. This means that physical addresses above 4GB (32 bits) cannot reliably be the source or destination of DMA operations. Therefore, the Red Hat Enterprise Linux 3 Update 2 kernel "bounces" all DMA operations to or from physical addresses above 4GB to buffers that the kernel pre-allocated below 4GB at boot time. This is likely to result in lower performance for IO-intensive workloads for Intel EM64T as compared to AMD64 processors.”
Although this shouldn't affect people that run with under 4GB of memory, this is an important point to note. If you do ever need the extra memory, you may take a performance hit. Unfortunately, we do not have over 4GB of DDR2 memory here today so we will not be able to test how much of a hit you would take if any"
The bottom line is that many believe (including myself) the physical addressing will be a significant problem, and many (including you) don't.
That's why I have requested that AT do an actual test...nothing like reality to settle a discussion...:-)
BTW, thanks for correcting my typo...
Dubb - Monday, February 14, 2005 - link
/taps fingers impatiently waiting on rendering benchmarks...which hopefully include (hint hint)
mental ray
brazil
renderman
Accord99 - Monday, February 14, 2005 - link
Your understanding of the IOMMU is wrong. Please refer to this thread:http://realworldtech.com/forums/index.cfm?action=d...
Also, the Xeon supports 36-bits.
Viditor - Monday, February 14, 2005 - link
Accord99 - "The IOMMU is only used for peripherals that don't support 64-bit addressing"The IOMMU is a memory mapping unit sitting between the I/O bus and physical memory. While the memory controller of the Xeon can address 64bit, it uses PAE to do so because current chipsets only address 32 bits. The on-die memory controller for AMD64 chips address 40 bits...
Accord99 - Monday, February 14, 2005 - link
The hardware IOMMU has no impact on the Xeon's ability to flat address >4GB of memory. The IOMMU is only used for peripherals that don't support 64-bit addressing, ie USB 2.0 cards, EIDE controllers, soundcards, some network controllers and will reduce IO performance for these devices. High-end 64-bit SCSI controllers, gigabit network controllers and newer SATA controllers all support 64-bit addressing and run at full performance.Viditor - Monday, February 14, 2005 - link
One other request (if it's possible)...Just so we can get a well-rounded view on the results, is it possible for you to do a Solaris/Oracle and Linux/MySQL (or Linux/Postgres) test?
I realise that I'm asking a lot, but if you have the time...:-)