Linux Database Server CPU Comparison
by Johan De Gelas on June 17, 2005 12:05 AM EST- Posted in
- IT Computing
Benchmarks MySQL 4.0.18: Intel versus AMD
It must be said that the MySQL results had a large margin of error (3% - 4%) compared to DB2, especially at high levels of concurrency.
Here is our MySQL configuration:
Read_buffer=2GB
Port=3306
socket = /var/lib/mysql/mysql.sock
skip-locking
set-variable = max_user_connections= 2000
set-variable = max_connections= 2000
key_buffer=2G
Read_buffer=2G
table_cache=1024
tmp_table=128M
max_heap_table=256M
read_rnd_buffer = 64M
thread_cache=16
net_buffer_length=16k
The " query cache" was off, as we wanted to test worst case performance. In some cases, the query cache was able to push a single Xeon to 1000 queries per second, and the CPU was still capable of doing more, as the CPU load was at 50% - 70%. At 1000 queries/s and more, other bottlenecks started to kick in, such as the latency of the network driver, the operating system and so on.
All numbers are expressed in queries per second. All concurrency tests below 5 are not reliable enough to make any firm conclusion as the margin of error is much higher.
| Concurrency | Dual Xeon (Gallatin) with L3 cache |
Single Xeon (Gallatin) with L3 cache |
Dual Xeon (Nocona) with HT |
Single Xeon (Nocona) with HT |
Dual Xeon (Irwindale) 3.6GHz with HT |
Dual Core Intel 3.2GHz |
Dual Opteron 250 2.4Ghz |
Single Opteron 250 2.4GHz |
Single Opteron 252 2.6 GHz |
| 1 | 243 | 248 | 280 | 277 | 286 | 233 | 290 | 298 | 319 |
| 2 | 357 | 317 | 423 | 338 | 450 | 344 | 438 | 370 | 399 |
| 5 | 466 | 356 | 473 | 358 | 497 | 442 | 543 | 435 | 470 |
| 10 | 505 | 361 | 521 | 375 | 517 | 487 | 629 | 465 | 502 |
| 20 | 496 | 350 | 531 | 371 | 545 | 507 | 670 | 455 | 498 |
| 35 | 508 | 355 | 555 | 371 | 506 | 490 | 665 | 470 | 507 |
| 50 | 497 | 348 | 526 | 368 | 495 | 502 | 669 | 472 | 508 |
| AVG | 494 | 354 | 521 | 368 | 512 | 486 | 635 | 460 | 497 |
| MAX | 508 | 361 | 555 | 375 | 545 | 507 | 670 | 472 | 508 |
Those were the raw numbers. Let us now analyse this...
| Concurrency | Dual versus Single Xeon Galatin | Dual versus Single Xeon Nocona/ Irwindale | Dual Opteron 250 vs Single |
| 1 | -2% | 1% | -3% |
| 2 | 12% | 25% | 18% |
| 5 | 31% | 32% | 25% |
| 10 | 40% | 39% | 35% |
| 20 | 42% | 43% | 47% |
| 35 | 43% | 50% | 41% |
| 50 | 43% | 43% | 42% |
| AVG | 40% | 41% | 38% |
MySQL ISAM is an incredibly fast database engine in our benchmark situation: it handles the same workload about twice as fast as DB2. I have to emphasize "our benchmark situation" because we cannot forget that our workload is mainly about reading the database and not writing. And of course, it must be said that the MySQL ISAM engine does less work on each query than DB2; it does not support transaction-safe (ACID compliant) commit, rollback, and crash recovery capabilities.
MySQL, as we have also noticed 6 months ago, doesn't seem to scale as well as DB2. At best, you get a 40% - 45% performance increase when the concurrency level is high enough. When we move to quad CPUs, we only get a 20% - 30% increase while DB2 still offers a 70% increase. The better scaling of DB2 means that with enough CPUs, it runs almost as fast as the MySQL ISAM engine, and offers all the transaction-safe capabilities as a bonus.
Let us check if the architectural differences between the CPUs make a difference . Again, don't pay too much attention to the results of the lower concurrency levels.
| Concurrency | Dual Xeon Irwindale versus Nocona (3,6 GHz) | Xeon Nocona (3,6 GHz) vs Galatin (3,06) | Opteron 2.6 vs Nocona 3.6 | Opteron 2.6 vs Pentium-D | Xeon Nocona 3,6 GHz vs Pentium-D |
| 1 | 2% | 12% | 15% | 37% | 19% |
| 2 | 6% | 7% | 18% | 16% | -2% |
| 5 | 5% | 1% | 31% | 6% | -19% |
| 10 | -1% | 4% | 34% | 3% | -23% |
| 20 | 3% | 6% | 34% | -2% | -27% |
| 35 | -9% | 5% | 37% | 4% | -24% |
| 50 | -6% | 6% | 38% | 1% | -27% |
| AVG | -2% | 4% | 35% | 2% | -24% |
| MAX | -2% | 4% | 36% | 0% | -26% |
The bigger L2-cache of the Xeon Irwindale did nothing more than compensate for the slightly higher latency of the L2-cache. The Xeon Irwindale and Nocona perform alike.
MySQL, unless you get the special Intel Compiler optimized version, remains the stronghold of the Opteron. The fastest (single core) Opteron outperforms the best Intel CPU by a 35% margin. We didn't use the Intel compiler version as we have reason to believe that this version is not used a lot in the real world. We might try it out in a future article.
The relatively limited scaling also means that high clocked single CPUs can be an interesting option. This is illustrated by the Opteron 252 2.6 GHz, which outperforms the dual core Pentium-D 3.2 GHz by a small margin.
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JohanAnandtech - Saturday, June 18, 2005 - link
Mino, thanks for pointing that out. Query cache enabling has nothing to do with "stressful". It has to do with accelarting a few queries that are run over and over again. Which is very interesting for reducing the response time of a website serving up the last article, but which is not limited by CPU power at all.JohanAnandtech - Saturday, June 18, 2005 - link
To the people who make a fuss about disabling the query cache: this has nothing to with the Opteron not performing well in that situation. Single Xeon: 980 queries/s. Dual xeon: 985 queries/s Opteron 250: 1020 queries/s . Get it now why I say "other bottlenecks started to kick in"?It impossible that a dual xeon can't outperform a single one in these tests. We tried to find the bottleneck and even used a quad opteron 850 as client. The client was not the problem. My bet is on the network latency, but I have no knowledge of tools to profile the complete machine. The disk was not the problem, we tested that. Network bandwidth neither. My bet is on the network latency, or even the OS as the bottleneck kicked in a lot sooner w kernel 2.4
mino - Friday, June 17, 2005 - link
#32 try to think for a moment"Because the Opteron can't perform that well in stressful situations you won't post the scores?"
If the CPU is not the bottleneck in the query cache scenario then why test the effect of CPU at all !!!
You reminded me friend of mine who "tested" effect the "FSB" has on A64 system NOT having an FSB at all !!! ;-)
Funny guy indeed.
And about an intel compiler not beeing used.
Like it or not, It IS a fact that it is not widely adopted especially among the target audience of this site an article.
BTW given the past experience intel compiler would produce better code even on AMD systems so don't be so sure! Best code for K7 is made by intelcc set to PIII config. Albeit it does not use 3DNow! functionality at all.
ElMoIsEviL - Friday, June 17, 2005 - link
I think I have to agree with #20, as much as I am un-biased I feel this test was doctored by AMD... it ressembles the tests we see released by Apple often..."We didn't use the Intel compiler version as we have reason to believe that this version is not used a lot in the real world. We might try it out in a future article."
Translation, "with the intel compiler AMD lost so being a marketing force for AMD we opted not to post those scores".
and also as was mentioned before...
""The " query cache" was off, as we wanted to test worst case performance. In some cases, the query cache was able to push a single Xeon to 1000 queries per second, and the CPU was still capable of doing more, as the CPU load was at 50% - 70%."
Why not?
Because the Opteron can't perform that well in stressful situations you won't post the scores?
Seriously.. this test is the biggest load of BS I have ever read... and I'm a current AMD adopter.
JohanAnandtech - Friday, June 17, 2005 - link
Viditor, it is possible that the IOMMU might have to do something with it.The IOMMU is a memory mapping unit sitting between the I/O bus and physical memory.
Memory mapping is AFAIK only necessary if a certain device (PCI devices come to mind) can not do a 64 bit DMA. Now it seems that almost everything inside the newest Intel southbridges can do 64 bit DMA.
So the IOMMU can only play a role when the driver is a 32 bit only, and the memory mapping has to happen. Now I would think that Intel would have an advantage here with their ultra modern southbridges. There might be a device that I am overlooking of course. Maybe our SCSI controller... But I don't think so.
Viditor - Friday, June 17, 2005 - link
Johan, if you're still reading (great article BTW)...A question I have had for quite awhile now is what effect the IOMMU has on these tests.
The reasons I'm asking are
1. I noticed that there was quite a disparity between the AMD and Intel 64bit performance (which you mentioned).
2. I know that one difference between the 2 platforms is that AMD has a hardware IOMMU (of sorts) and Intel (at present) does not.
3. I saw a thread last year with Linus T mentioning this quite a bit. He seemed to think that this would impair the EM64T substantially...
Your thoughts?
JohanAnandtech - Friday, June 17, 2005 - link
If your database is running many "identical databases".... I meant "queries"JohanAnandtech - Friday, June 17, 2005 - link
Juhl: It was 2.6.12rc5.Viditor: thanks for the helpful comment. Indeed, if you turn on the query cache, your CPU is doing very little.
Everybody else: note the "identical" word in viditor's quote. If your database is running many identical databases, than you are not going to spend time reading this kind of article: you simply buy the cheapest decent server. Any CPU today can run 1000s of querries if everything comes out the query cache.
Running benchmarks with the query cache on is simply not interesting. The query cache is all about accelerating the IDENTICAL queries that are run from time to time. You might reserve a bit of RAM to make sure that the most common queries (getting the latest article of a website for example) are run faster.
But those numbers don't tell you anything about the load that your server is going to be able to take. You want worst case performance numbers!
Viditor - Friday, June 17, 2005 - link
Questar - the reason the query cache was turned off (guessing here) is to more reasonably simulate a real-world test. Obviously in this test, the same queries are repeated quite often. But that is not usually the case in the real world...For those who don't know what the heck a "query cache" is:
"the query cache stores the text of a SELECT query together with the corresponding result that was sent to the client. If the identical query is received later, the server retrieves the results from the query cache rather than parsing and executing the query again"
Questar - Friday, June 17, 2005 - link
#23,We don't know, it specifically says Xeon. We don't have any idea what happens on an Opteron.