On Tue, 27 Oct 2009, Andrew Morton wrote:
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index dfa4362..7f2aa3e 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1769,7 +1769,7 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
> > * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
> > */
> > alloc_flags &= ~ALLOC_CPUSET;
> > - } else if (unlikely(rt_task(p)))
> > + } else if (unlikely(rt_task(p)) && !in_interrupt())
> > alloc_flags |= ALLOC_HARDER;
> >
> > if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
>
> What are the runtime-observeable effects of this change?
>
Giving rt tasks access to memory reserves is necessary to reduce latency,
the privilege does not apply to interrupts that subsequently get run on
the same cpu.
> The description is a bit waffly-sounding for a -stable backportable
> thing, IMO. What reason do the -stable maintainers and users have to
> believe that this patch is needed, and an improvement?
>
Allowing interrupts to allocate below the low watermark when not
GFP_ATOMIC depletes memory reserves; this fixes an inconsistency
introduced by the page allocator refactoring patchset that went into
2.6.31.
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