Benchmarks: AMD64 vs i386 on Dual 246 Opteron
Matthew.Sullivan at canberra.edu.au
Mon Aug 1 23:45:04 GMT 2005
> ray at redshift.com wrote:
>> Freebsd-AMD64 list:
>> I recently completed benchmarking an evaluation server provided to us
>> by our
>> hardware vendor in order to see if switching our cluster from Xeon based
>> machines to AMD based machines was worth while/cost effective
>> The machine provided was a Dual Opteron 246 using the Tyan S2881
>> It had 4GB or ram and included a single SATA hard drive.
>> I initially loaded FreeBSD 5.4 AMD64 on the machine, recompiled the
>> kernel, etc.
>> and applied all the normal tweaks to apache, PHP, etc. The machine,
>> faster than our single 2.4 Ghz Xeon's, wasn't all that much faster
>> (maybe only
>> 10 to 15 percent).
>> After speaking with AMD and doing further benchmarks, I was about to
>> give up on
>> AMD and return the machine. However, at the last minute, an engineer
>> from AMD
>> suggested that perhaps loading the 32 bit version of FreeBSD (aka
>> i386) might
>> improve performance, since it was possible that the overhead from 64 bit
>> pointers was causing the machine to run slower than expected. He also
>> that the AMD should be running about 3 to 4 times faster than the
>> single Xeon.
>> While this sounded like a long shot, I loaded FreeBSD 5.4 i386 on the
>> and after applying the exact same configuration to the OS, Apache, PHP
>> MySQL, re-ran the benchmarks. Much to my surprise, just changing the
>> OS from 64
>> bit to 32 bit caused the machine to double in speed. The results are
>> in an Excel spreadsheet. So the exact same machine, running the
>> configuration, performed roughly twice as fast when running FreeBSD
>> 5.4 i386 vs
>> FreeBSD 5.4 AMD64. Something about this seems so wrong to me :-)
>> In speaking with one person off the list here, I was told that the
>> FreeBSD AMD64
>> branch has actually been cleaned up substantially over the i386 code. So
>> naturally I was expecting much better performance from a 64 bit
>> machine running
>> the AMD64 code than the "older" i386 code. I had also originally
>> expected that
>> since this branch [the AMD64 branch] was specifically built around the
>> CPU's, that it should run the best (and thus the fastest) on the AMD
>> CPU's. However, just the contrary turned out to be the case in
>> I'm wondering if anyone has any comments or thoughts on this? The
>> benchmarks show transactions per second across localhost using Apache
>> AB on the
>> same machine. The first tests are with plain text files from 64 bytes
>> to 50K in
>> size. The next group is using a small and medium size PHP program.
>> The final
>> set relate to MySQL inserts, selects and updates. As you can see from
>> the data,
>> the exact same machine runs about twice as fast just by switching the
>> OS from
>> AMD64 to i386. But why?
>> The only answer I have so far as to why this may be the case is that
>> i386 uses 32 bit pointers which the CPU(s) can handle faster (thus
>> less overhead
>> for the CPU). But it still seems odd to me that if FreeBSD AMD64 is
>> specifically for the 64 bit CPU, why doesn't the machine perform
>> better when
>> running it?
>> I'm also wondering if there is a compiler switch on AMD64 that could
>> be used
>> (perhaps in /etc/make.conf or something) that would force the AMD64
>> version to
>> run in 32 bit mode only - since that would be an interesting
>> comparison as well.
>> I welcome any/all comments, suggestions, insight.
> Good morning. I'm very NEW to the list and NEW to 64bit systems. I
> installed 5.4-R (i386) on my dual AMD64 Opteron 2.0g (1mb cache) with 1g
> ram and 4 X 160 (raid10) sata drives server. I was blazing fast, I think
> the first kernel recompile was 10 minutes or so "time make buildkernel
> KERNCONF=KERNEL" I was shocked to see how fast it was. (I know you
> tested with php/etc...) Well, like an idiot, I was thinking I could use
> the i386 install disc to get the 64bit. Eh.. no go. I then grabbed the
> boot only 64bit from FreeBSD's ftp site and loaded it. Base install of
> course. When I did the "first compile" I yet again. was surprised.
> 6:29:xx!!! Fastest I've ever seen a kernel compile and that was with ONE
> cpu. (Had to compile in SMP.) Man, never had a system that was this fast.
> Needless to say, I think the 64bit out performs the 32bit OSes. Then
> again, I'm not as technical as most of you all are, I'm just chimming in
> from a "different" side.
> Please, put me in my place if need be. :)
This echos my experiences...
Further to that I have seen some amazing feats of sheer processing power -
processing out Postfix queues of >5k messages (with inline virus checking) on a
single AMD64 processor in under 5 minutes (most messages being delivered through
a perl script). Mailing lists of 500+ people getting getting processed _and_
delivered in under 20 seconds from first accept to last delivery (450+ users on
the list were remote Internet users). As a mail server with inline virus
scanning I have no qualms with it receiving 50 messages per second - infact
there is a 22M Uplink to the net, so far it has kept up with everything to the
point of the 22M being full.
Asus K8S M/B
Dual 160G SATA (RAID1 config).
IT Security Manager
The University of Canberra
A member of the Australian Association for the Abolition of
Acronym Abuse, Regional Group Headquarters, Strategic and
Tactical Operations Planning (AAAAARGHSTOP).
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