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From: Andrew Theurer <habanero@us.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>
Subject: Re: Linux 2.4.19-rc3 (hyperthreading)
Date: Mon, 29 Jul 2002 14:54:30 -0500	[thread overview]
Message-ID: <200207291454.30076.habanero@us.ibm.com> (raw)

I would caution against having hyperthreading on by default in the 2.4.19 
release.  I am seeing a significant degrade in network workloads on P4 with 
hyperthreading on.  On 2.4.19-pre10, I get 788 Mbps on NetBench, but on 
2.4.19-rc1 (and probably rc3, should know in an hour), I get 690 Mbps.  It is 
clearly a hyperthreading/interrupt routing issue.  On this system (4 x P4), 
with no hyperthreading, there is enough CPU to handle all interrupts on CPU0 
(this is where all ints go by default).  With hyperthreading on, I get "1/2" 
of a CPU for interrupt processing.  What ends up happenning is that CPU0 is 
at 100%, while CPU1-CPU7 are at 75%.  Now I know the "noth" is available, but 
since hyperthreading is not proven to give a performance boost to more than 
1/2 of the common workloads for linux users (or is it? who has done tests?), 
I'd like to see this default behavior reversed, and still use acpismp=force 
to enable hyperthreading.  

Also, If anyone has performance results for their workloads showing a boost 
with hyperthreading, I would really like to know.  

-Andrew Theurer



<<So here goes rc3. Another -rc is going to come only in the case of really
critical problem(s).

I'm attaching the rc2->rc3 changelog only because the full changelog got
too big (I guess thats why my -rc2 announce mail didnt go to lk).>>



             reply	other threads:[~2002-07-29 19:59 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-07-29 19:54 Andrew Theurer [this message]
2002-07-29 21:28 ` Linux 2.4.19-rc3 (hyperthreading) Alan Cox
2002-07-29 20:38   ` Andrea Arcangeli
2002-07-29 23:45     ` Andrea Arcangeli
2002-07-29 23:51       ` Rik van Riel
2002-07-30  0:04         ` Andrea Arcangeli
2002-07-30  0:09         ` J.A. Magallon
2002-07-30  0:32           ` Andrea Arcangeli
2002-07-31  3:08           ` Bill Davidsen
2002-07-31 12:43             ` Rik van Riel
2002-07-31 14:16               ` Sam Vilain
2002-08-01 18:29                 ` Ingo Oeser
2002-07-29 20:58   ` Andrew Theurer
2002-07-30  0:37     ` Alan Cox
2002-07-29 23:42       ` Andrew Theurer
2002-07-30  0:56         ` James Bourne
2002-07-30  0:47     ` James Bourne
2002-07-30  1:15       ` Andrew Theurer
2002-07-30  3:09         ` James Bourne

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