From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] mm: remove lru_add_drain_all in alloc_contig_range
Date: Tue, 9 Feb 2021 20:03:32 +0100 [thread overview]
Message-ID: <20210209190332.GA3363@localhost.localdomain> (raw)
In-Reply-To: <accc057c-e639-7510-f722-4a4d166c80b6@redhat.com>
On Tue, Feb 09, 2021 at 07:17:59PM +0100, David Hildenbrand wrote:
> On 09.02.21 18:50, Minchan Kim wrote:
> > __alloc_contig_migrate_range already has lru_add_drain_all call
> > via migrate_prep. It's necessary to move LRU taget pages into
> > LRU list to be able to isolated. However, lru_add_drain_all call
> > after __alloc_contig_migrate_range is called is pointless.
> >
> > This patch removes it.
> >
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > mm/page_alloc.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 6446778cbc6b..f8fbee73dd6d 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -8603,8 +8603,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> > * isolated thus they won't get removed from buddy.
> > */
> > - lru_add_drain_all();
> > -
> > order = 0;
> > outer_start = start;
> > while (!PageBuddy(pfn_to_page(outer_start))) {
> >
>
> I was expecting some magical reason why this is still required but I am not
> able to find a compelling one. Maybe this is really some historical
> artifact.
>
> Let's see if other people know why this call here still exists.
I also stumbled upon this while working on adding hugetlb support for
alloc_acontig_range [1].
I have to confess I puzzled me a bit.
I saw it going back to when the function was first introduced by
commit 041d3a8cdc18dc375a128d90bbb753949a81b1fb
Author: Michal Nazarewicz <mina86@mina86.com>
Date: Thu Dec 29 13:09:50 2011 +0100
mm: page_alloc: introduce alloc_contig_range()
It does not make much sense to me. At this point our pages are free, so
we do not care about LRU handling here.
But I might be missing something.
[1] https://lore.kernel.org/linux-mm/20210208103935.GA32103@linux/T/#md651fc6e73c656105179382f92f8b2d6073051d1
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-02-09 21:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 17:50 [PATCH] mm: remove lru_add_drain_all in alloc_contig_range Minchan Kim
2021-02-09 18:17 ` David Hildenbrand
2021-02-09 19:03 ` Oscar Salvador [this message]
2021-02-10 12:17 ` Vlastimil Babka
2021-02-10 12:23 ` Michal Hocko
2021-02-10 14:27 ` Oscar Salvador
2021-02-10 15:58 ` Minchan Kim
2021-02-10 12:13 ` Vlastimil Babka
2021-02-10 14:28 ` Oscar Salvador
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