Re: ZONE_PADDING wastes 4 bytes of the new cacheline

Nick Piggin
2004-10-23T04:36:34Z

Andrea Arcangeli wrote:
> On Fri, Oct 22, 2004 at 01:02:24PM +1000, Nick Piggin wrote:
>
>>I don't agree, there are times when you need to know the bare pages_xxx
>>watermark, and times when you need to know the whole ->protection thing.
>

[snip]

>
> I don't see any benefit in limiting the high order, infact it seems a
> bad bug. If something you should limit the _small_ order, so that the
> high order will have a slight chance to succeed. You're basically doing
> the opposite.
>

You need the order there so someone can't allocate a huge amount
of memory and deplete all your reserves and crash the system.

For day to day running, it should barely make a difference because
the watermarks will be an order of magnitude larger.

> The pages_low is completely useless too for example and it could go.
> pages_min has some benefit for some more feature 2.6 provides (that
> could be translated in more watermarks, to separate the "settings of
> the watermarks" from the alloc_page user of the watermarks).
>

AFAIKS, pages_min, pages_low and pages_high are all required for
what we want to be doing. I don't see you you could remove any one
of them and still have everything functioning properly....

I haven't really looked at 2.4 or your patches though. Maybe I
misunderstood you.