Re: [RFC v2 00/34] SLUB: reduce irq disabled scope and make it RT compatible

From: Mike Galbraith
Date: Sun Jul 04 2021 - 01:43:14 EST

On Sat, 2021-07-03 at 17:47 +0200, Mike Galbraith wrote:
> On Sat, 2021-07-03 at 09:24 +0200, Mike Galbraith wrote:
> > It also appears to be saying that there's something RT specific to
> > stare at in addition to the list_lock business.
> The what is ___slab_alloc() consuming 3.9% CPU in tip-rt-slub whereas
> it consumes < 1% in both tip-rt (sans slub patches) and tip-slub.
> The why remains to ponder.

Ignoring odd distribution in the profile (red herring whackable via
prefetch games), and removing perf/debug options from the picture, the
remaining RT specific cost is just that of forced slow path. For
hackbench in my little box, it adds up to right at 3%.