> > Nope, have you checked the output of /sys/kernel/slab/.../order when
> > running slub? On my workstation 127 out of 316 caches have order-2 or
> > higher by default.
> >
>
> Well, this is still on the side of my argument, since this is still a majority
> of them being low ordered.
Ok, so what happens if I pass slub_min_order=2 on the command line? We
never retry?
> The code here does not necessarily have to retry -
> if I understand it correctly - we just retry for very small allocations
> because that is where our likelihood of succeeding is.
>
Well, the comment for NR_PAGES_TO_RETRY says
/*
* We need a number that is small enough to be likely to have been
* reclaimed even under pressure, but not too big to trigger unnecessary
* retries
*/
and mmzone.h says
/*
* PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
* costly to service. That is between allocation orders which should
* coalesce naturally under reasonable reclaim pressure and those which
* will not.
*/
#define PAGE_ALLOC_COSTLY_ORDER 3
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