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SubjectRe: [PATCH v2 03/20] mm, hugetlb: fix subpool accounting handling
On Mon, Aug 26, 2013 at 06:31:35PM +0530, Aneesh Kumar K.V wrote:
> Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:
>
> > On Thu, Aug 22, 2013 at 12:38:12PM +0530, Aneesh Kumar K.V wrote:
> >> Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:
> >>
> >> > Hello, Aneesh.
> >> >
> >> > First of all, thank you for review!
> >> >
> >> > On Wed, Aug 21, 2013 at 02:58:20PM +0530, Aneesh Kumar K.V wrote:
> >> >> Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:
> >> >>
> >> >> > If we alloc hugepage with avoid_reserve, we don't dequeue reserved one.
> >> >> > So, we should check subpool counter when avoid_reserve.
> >> >> > This patch implement it.
> >> >>
> >> >> Can you explain this better ? ie, if we don't have a reservation in the
> >> >> area chg != 0. So why look at avoid_reserve.
> >> >
> >> > We don't consider avoid_reserve when chg != 0.
> >> > Look at following code.
> >> >
> >> > + if (chg || avoid_reserve)
> >> > + if (hugepage_subpool_get_pages(spool, 1))
> >> >
> >> > It means that if chg != 0, we skip to check avoid_reserve.
> >>
> >> when whould be avoid_reserve == 1 and chg == 0 ?
> >
> > In this case, we should do hugepage_subpool_get_pages(), since we don't
> > get a reserved page due to avoid_reserve.
>
> As per off-list discussion we had around this, please add additional
> information in commit message explaining when we have
> avoid_reserve == 1 and chg == 0

Okay!

>
> Something like the below copied from call site.
>
> /* If the process that created a MAP_PRIVATE mapping is about to
> * perform a COW due to a shared page count, attempt to satisfy
> * the allocation without using the existing reserves
> */
>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Thanks.


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