On Friday 12 December 2008 13:47, Andrew Morton wrote:

On Fri, 12 Dec 2008 12:31:33 +1000 Nick Piggin [off-list ref] 

wrote:

quoted

On Friday 12 December 2008 07:43, Andrew Morton wrote:

quoted

On Thu, 11 Dec 2008 20:28:00 +0000

quoted

 Do they actually cross the page boundaries?

Some flavours of slab have at times done an order-1 allocation for
objects which would fit into an order-0 page (etc) if it looks like
that will be beneficial from a packing POV.  I'm unsure whether that
still happens - I tried to get it stamped out for reliability reasons.

Hmph, SLUB uses order-3 allocations for 832 byte sized objects
by default here (mm struct).

That sucks, but at least it's <= PAGE_ALLOC_COSTLY_ORDER.

Which is somewhat arbitrary a value. order-1 is costly compared to
order-0...

After running my system here for a while and doing various things
with it, I have the ability to allocate 898 order-0 pages (3592K),
or 36 order-3 pages (1152K).

Not as bad as I expected, but the system's only been up for an hour,
and not exactly doing anything unusual (and it has nearly 30MB free,
out of 4GB).

It's fortunate that everyone has more than 128GB of memory.

And that SLAB still works quite well :)