Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

[Martin J. Bligh]

--Linus Torvalds <torvalds@xxxxxxxx> wrote (on Thursday, November 03, 2005 10:44:14 -0800):

> 
> 
> On Thu, 3 Nov 2005, Martin J. Bligh wrote:
>> > 
>> > These days we have things like per-cpu lists in front of the buddy 
>> > allocator that will make fragmentation somewhat higher, but it's still 
>> > absolutely true that the page allocation layout is _not_ random.
>> 
>> OK, well I'll quit torturing you with incorrect math if you'll concede
>> that the situation gets much much worse as memory sizes get larger ;-)
> 
> I don't remember the specifics (I did the stats several years ago), but if 
> I recall correctly, the low-order allocations actually got _better_ with 
> more memory, assuming you kept a fixed percentage of memory free. So you 
> actually needed _less_ memory free (in percentages) to get low-order 
> allocations reliably.

Possibly, I can redo the calculations easily enough (have to go for now,
but I just sent the other ones). But we don't keep a fixed percentage of
memory free - we cap it ... perhaps we should though?

M.

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