On Fri, Oct 14, 2016 at 03:35:59PM +0100, Tvrtko Ursulin wrote:
> On 14/10/2016 14:53, Chris Wilson wrote:
> >>>We do pass NORETRY | NOWARN for the higher order allocations, so it
> >>>shouldn't be as bad it seems?
> >>I don't know for sure without looking into the implementation
> >>details. But I assumed even with NORETRY it does some extra work to
> >>try and free up the space. And if it fails, and we ask for it again,
> >>it is just doing that extra work for nothing. Because within a
> >>single allocation it sounds unlikely that something would change so
> >>dramatically that it would start working.
> >iirc, NORETRY means abort after failure. In effect, it does
> >2 attempts from the freelist, a direct reclaim, and may then repeat
> >if the task's allowed set of nodes were concurrently changed.
> Do you think it makes sense doing all that after it started failing,
> within our single get_pages allocation?

I was thinking about skipping the DIRECT_RECLAIM for high order, but it
seems like that is beneficial for THP, so I'm presuming it should also
be for ourselves. Trimming back max_order seems sensible, but I still
like the idea of taking advantage of contiguous pages where possible
(primarily these will be used for ringbuffers and shadow batches).

Chris Wilson, Intel Open Source Technology Centre
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