Re: [PATCH/RFCv4 0/6] The Contiguous Memory Allocator framework

[Minchan Kim]

On Thu, Aug 26, 2010 at 7:06 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Thu, 2010-08-26 at 18:29 +0900, Minchan Kim wrote:
>> As I said following mail, I said about free space problem.
>> Of course, compaction could move anon pages into somewhere.
>> What's is somewhere? At last, it's same zone.
>> It can prevent fragment problem but not size of free space.
>> So I mean it would be better to move it into another zone(ex, HIGHMEM)
>> rather than OOM kill.
>
> Real machines don't have highmem, highmem sucks!! /me runs

It's another topic.
I agree highmem isn't a gorgeous. But my desktop isn't real machine?
Important thing is that we already have a highmem and many guys
include you(kmap stacking patch :))try to improve highmem problems. :)

>
> Does cross zone movement really matter, I though these crappy devices
> were mostly used on crappy hardware with very limited memory, so pretty
> much everything would be in zone_normal.. no?

No. Until now, many embedded devices have used to small memory. In
that case, only there is a DMA zone in system. But as I know, mobile
phone starts to use big(?) memory like 1G or above sooner or later. So
they starts to use HIGHMEM. Otherwise, 2G/2G space configuration.
Some embedded device uses many thread model to port easily from RTOS.
In that case, they don't have enough address space for application if
it uses 2G/2G model.

So we should care of HIGHMEM in embedded system from now on.

>
> But sure, if there's really a need we can look at maybe doing cross zone
> movement.
>


-- 
Kind regards,
Minchan Kim
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