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Date:      Tue, 14 Mar 2006 19:14:54 -0300
From:      JoaoBR <joao@matik.com.br>
To:        freebsd-amd64@freebsd.org
Subject:   Re: amd64 slower than i386 on identical AMD 64 system?
Message-ID:  <200603141914.54442.joao@matik.com.br>
In-Reply-To: <20060314112625.09a3ac2c.wmoran@collaborativefusion.com>
References:  <200603140740.38388.joao@matik.com.br> <200603141710.12822.kono@kth.se> <20060314112625.09a3ac2c.wmoran@collaborativefusion.com>

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On Tuesday 14 March 2006 13:26, Bill Moran wrote:

> We've been doing some tests here (on Dell Poweredge 2850) and haven't
> done extensive tweaking (have tried different -O or any other compile
> flags)
>

that is good I think because even if it could give certain benefit in certa=
in=20
cases the base system should run as is. Special configs can be necessary fo=
r=20
special application but should not be necessary to get a standard setup=20
suitable for what it was designed

> So far, our conclusion is that running amd64 binaries on an amd64
> kernel is slower than ia32 binaries on an ia32 kernel.  We're
> comparing identical 2850 hardware, both kernels built with SMP
> (although there seem to be some issues related to running SMP on
> amd64)
>

I can confirm this too
SMP amd64s are having constant crashes when running >2GB and <4GB of RAM.
In order not getting anything wrong I am talking about X2-SMP mono-chip-MBs
this is not happening on dual-chip-MB with two separate processors.
I run the same hardware as UP-amd64 and it never crashes
Since this crashes are more frequent with IPI_PREEMPTION I have now some=20
servers under test running without PREEMPTION at all and appearently the=20
crashes are gone
Overall the amd64-SMP kernels running on X2 processors are extermly sensiti=
ve=20
to non polling NICs and are crashing often. The overall performance also is=
=20
bad.=20
Soon I change this cards into polling ones, seems XL is best, I do not have=
=20
crashes anymore.=20
=46unny that single 64bit AMDs are running fine with non polling NICs even =
when=20
running a SMP enabled kernel. Soon I put back the X2 ... boom.

> We've been using ubench and pgbench (since these will be PostgreSQL
> servers) to test.  We're seeing that the 64b stuff runs just a bit
> slower.  We're also seeing that the amd64 doesn't seem to scale up
> to using more than one processor, but that's an issue under investigation
> (see other thread on this list)

this I can not confirm, I get SMP X2-amds with ULE and 4BSD running on both=
=20
cpus, same for dual-chip-MBs
But I can not say anything about PGSQL at all
My servers are cache servers in first place and I have some web and mail=20
server running amd64 and the cpu scheduling seems to work well. Overall I=20
have the impression that the ULE scheduler is giving better performance on =
a=20
machine with more than 2MB/s going through

Jo=E3o









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