Re: kmem caches and the cache line size

[Lars Reichardt <lars%paradoxon.info@localhost>]

On Fri, 24 Jan 2020 11:09:51 +0000
Andrew Doran <ad%netbsd.org@localhost> wrote:

> Hi,
> 
> This zero pads the cache names to be more readable in vmstat output,
> and avoids creation of caches where the item size is not a factor or
> multiple of the cache line size.
> 
> 	http://www.netbsd.org/~ad/2020/kmem.diff
> 
> This gives me a repeatable 1-2% speed up on compile jobs on my test
> system, means that __aligned(COHERENCY_UNIT) can be used more easily
> in structures allocated with kmem_alloc(), and permits removal of a
> bunch of padding and rounding done during allocation.
> 
> Comments?
> 
> Cheers,
> Andrew

Hi,

looks good to me.

Just a thought I have no numbers to back that...
It might be worse a try to drop the small 8 byte cache as that
would half the size of the kmem_cache array for lookups,
the 24, 40, 56 and 80 byte (etc) ones should be gone with your changes
anyway.
(1024 => 512 bytes with 64 bit pointers)

Assuming COHERENCY_UNIT of either 32 (mips) 64 (most) and 128 ia64.


Lars


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