Re: Avoiding external fragmentation with a placement policy Version 12

Martin J. Bligh
2005-06-03T13:57:42Z

>>> Actually, even with TSO enabled, you'll get large order
>>> allocations, but for receive packets, and these allocations
>>> happen in software interrupt context.
>>
>> Sounds like we still need to cope then ... ?
>
> Sure. Although we should try to not use higher order allocs if
> possible of course. Even with a fallback mode, you will still be
> putting more pressure on higher order areas and thus degrading
> the service for *other* allocators, so such schemes should
> obviously be justified by performance improvements.

My point is that outside of a benchmark situation (where we just
rebooted the machine to run a test) you will NEVER get an order 4
block free anyway, so it's pointless. Moreover, if we use non-contig
order 0 blocks, we can use cache hot pages ;-)

M.