From: Andrew Morton <akpm@linux-foundation.org>
To: Joonsoo Kim <js1304@gmail.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@kernel.org>,
Vlastimil Babka <vbabka@suse.cz>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
kernel-team@lge.com, Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH for v5.9] mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs
Date: Tue, 25 Aug 2020 17:42:57 -0700 [thread overview]
Message-ID: <20200825174257.5b48a5dd24b5e08a915b101e@linux-foundation.org> (raw)
In-Reply-To: <CAAmzW4MYQsRoR-q8tUmwPYLvCbiMq_zt19_AgorAQHnbwnu37g@mail.gmail.com>
On Tue, 25 Aug 2020 14:34:32 +0900 Joonsoo Kim <js1304@gmail.com> wrote:
> >
> > That's a bunch more code on a very hot path to serve an obscure feature
> > which has a single obscure callsite.
> >
> > Can we instead put the burden on that callsite rather than upon
> > everyone? For (dumb) example, teach __gup_longterm_locked() to put the
> > page back if it's CMA and go get another one?
>
> Hmm... Unfortunately, it cannot ensure that we eventually get the non-CMA page.
> I think that the only way to ensure it is to implement the
> functionality here. We can
> use 'unlikely' or 'static branch' to reduce the overhead for a really
> rare case but
> for now I have no idea how to completely remove the overhead.
Gee, there must be something? Provide the gup code with a special
entry point which takes the page straight from __rmqueue() and bypasses
the pcp lists?
next prev parent reply other threads:[~2020-08-26 0:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-25 4:59 js1304
2020-08-25 5:10 ` Andrew Morton
2020-08-25 5:34 ` Joonsoo Kim
2020-08-26 0:42 ` Andrew Morton [this message]
2020-08-26 5:21 ` Joonsoo Kim
2020-08-25 9:43 ` Vlastimil Babka
2020-08-26 5:12 ` Joonsoo Kim
2020-08-27 12:15 ` Vlastimil Babka
2020-08-27 13:35 ` Mel Gorman
2020-08-27 23:54 ` Joonsoo Kim
2020-09-25 4:59 ` Joonsoo Kim
2020-09-25 8:55 ` Vlastimil Babka
2020-09-25 8:58 ` Joonsoo Kim
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