Re: [RFC][PATCH 0/3] beat kswapd with the proverbial clue-bat

Nick Piggin
2004-09-05T10:13:59Z

Nick Piggin wrote:
> David S. Miller wrote:
>
>> On Sun, 05 Sep 2004 15:44:18 +1000
>> Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>>
>>
>>> So my solution? Just teach kswapd and the watermark code about higher
>>> order allocations in a fairly simple way. If pages_low is (say), 1024KB,
>>> we now also require 512KB of order-1 and above pages, 256K of order-2
>>> and up, 128K of order 3, etc. (perhaps we should stop at about order-3?)
>>
>>
>>
>> Whether to stop at order 3 is indeed an interesting question.
>>
>> The reality is that the high-order allocations come mostly from folks
>> using jumbo 9K MTUs on gigabit and faster technologies. On x86, an
>> order 2 would cover those packet allocations, but on sparc64 for example
>> order 1 would be enough, whereas on a 2K PAGE_SIZE system order 3 would
>> be necessary.
>>
>
> Yeah I see.
>

Hmm, and the crowning argument for not stopping at order 3 is that if we
never use higher order allocations, nothing will care about their watermarks
anyway. I think I had myself confused when that question in the first place.

So yeah, stopping at a fixed number isn't required, and as you say it keeps
things general and special cases minimal.