lkml.org 
[lkml]   [2021]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] mm: remove lru_add_drain_all in alloc_contig_range
    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

    \
     
     \ /
      Last update: 2021-02-09 22:56    [W:2.312 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site