>On Sun, Mar 19, 2006 at 10:38:36AM +0100, [EMAIL PROTECTED] wrote:
>> 
>> >I didn't try this on a laptop, but here are some numbers from a 2-way
>> >AMD system running in 64-bit mode showing how much memory gets used by
>> >the
>> >kernel in each case.
>> >
>> >NCPU    max_ncpus       kernel
>> >64      2               227MB
>> >21      21              231MB   - stock Nevada bits
>> >64      32              233MB
>> >64      64              242MB
>> 
>> Wow; that is quite a bit more than I expected (the strange "21" number
>> comes from ancient times when apparently 21 "sizeof (struct cpu)" fitten
>> on (a multiple of?) a page.
>> 
>> >So if max_ncpus is set to 64, we'd be throwing away 10Mb (or ~5% of
>> >all memory on a 256Mb laptop).  The difference between 21 and 32 is
>> >much smaller.
>> 
>> So what exactly uses this 256KB per CPU?
>
>kmem cpu caches are about 20k/cpu (64 bytes/cpu/cache * ~300 caches * max_ncpu)
>FMA looks like it's about 100k/cpu (ERPT_MAX_ERRS * max_ncpu * ERPT_DATA_SZ)

And they are all preallocated?  Sounds like a bug to me.

Casper
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