PAE Slowdown

[Jeff Kramer]

At 6:56 PM +0200 10/8/07, Ivan Voras wrote:
>Jeff Kramer wrote:
>>  Hey all,
>>
>>  I know that AMD64's the preferred way to run >4 gig systems, but I'm
>>  having a weird situation with 6.2-RELEASE-p8 and 6-STABLE as of last
>>  night.  When I compile the PAE kernel, my system performance drops like
>>  a rock.  It still boots and everything still runs, but for instance,
>>  running the Flops port my megaflops drop from the 950 MFLOPS range to 4
>>  MFLOPS.  It feels about as fast as a 486.
>
>Does vmstat -i show unusually high interrupt rates?

When it's running ok at idle (4 gig of ram):

interrupt                          total       rate
irq1: atkbd0                          77          0
irq16: twa0                         1084          3
irq17: atapci0                         1          0
irq19: fwohci0++                       3          0
irq20: em0                           161          0
cpu0: timer                       549165       1920
Total                             550491       1924

When it's slow at idle (8 gig of ram):

interrupt                          total       rate
irq1: atkbd0                          48          0
irq16: twa0                         1093          8
irq17: atapci0                         1          0
irq19: fwohci0++                       3          0
irq20: em0                           179          1
cpu0: timer                       241862       1950
Total                             243186       1961



-- 

Jeff Kramer
jeffk at well.com
http://www.jeffkramer.org/