From: Mel Gorman <mgorman@techsingularity.net>
To: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org,
linux-acpi@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Mike Rapoport <rppt@kernel.org>,
Scott Cheloha <cheloha@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v1 3/5] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate()
Date: Mon, 5 Oct 2020 09:20:49 +0100 [thread overview]
Message-ID: <20201005082049.GI3227@techsingularity.net> (raw)
In-Reply-To: <20201005065648.GO4555@dhcp22.suse.cz>
On Mon, Oct 05, 2020 at 08:56:48AM +0200, Michal Hocko wrote:
> On Fri 02-10-20 17:20:09, David Hildenbrand wrote:
> > On 02.10.20 15:24, Michal Hocko wrote:
> > > On Mon 28-09-20 20:21:08, David Hildenbrand wrote:
> > >> Page isolation doesn't actually touch the pages, it simply isolates
> > >> pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist.
> > >>
> > >> We already place pages to the tail of the freelists when undoing
> > >> isolation via __putback_isolated_page(), let's do it in any case
> > >> (e.g., if order <= pageblock_order) and document the behavior.
> > >>
> > >> Add a "to_tail" parameter to move_freepages_block() but introduce a
> > >> a new move_to_free_list_tail() - similar to add_to_free_list_tail().
> > >>
> > >> This change results in all pages getting onlined via online_pages() to
> > >> be placed to the tail of the freelist.
> > >
> > > Is there anything preventing to do this unconditionally? Or in other
> > > words is any of the existing callers of move_freepages_block benefiting
> > > from adding to the head?
> >
> > 1. mm/page_isolation.c:set_migratetype_isolate()
> >
> > We move stuff to the MIGRATE_ISOLATE list, we don't care about the order
> > there.
> >
> > 2. steal_suitable_fallback():
> >
> > I don't think we care too much about the order when already stealing
> > pageblocks ... and the freelist is empty I guess?
> >
> > 3. reserve_highatomic_pageblock()/unreserve_highatomic_pageblock()
> >
> > Not sure if we really care.
>
> Honestly, I have no idea. I can imagine that some atomic high order
> workloads (e.g. in net) might benefit from cache line hot pages but I am
> not sure this is really observable.
The highatomic reserve is more concerned that about the allocation
succeeding than it is about cache hotness.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2020-10-05 8:29 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 18:21 [PATCH v1 0/5] mm: place pages to the freelist tail when onling and undoing isolation David Hildenbrand
2020-09-28 18:21 ` [PATCH v1 1/5] mm/page_alloc: convert "report" flag of __free_one_page() to a proper flag David Hildenbrand
2020-09-28 20:11 ` Pankaj Gupta
2020-09-29 8:58 ` Wei Yang
2020-10-02 13:17 ` Michal Hocko
2020-10-02 13:41 ` Matthew Wilcox
2020-10-02 14:48 ` David Hildenbrand
2020-10-02 14:57 ` David Hildenbrand
2020-09-28 18:21 ` [PATCH v1 2/5] mm/page_alloc: place pages to tail in __putback_isolated_page() David Hildenbrand
2020-09-28 20:38 ` Pankaj Gupta
2020-09-29 9:10 ` Wei Yang
2020-10-02 13:19 ` Michal Hocko
2020-09-28 18:21 ` [PATCH v1 3/5] mm/page_alloc: always move pages to the tail of the freelist in unset_migratetype_isolate() David Hildenbrand
2020-09-28 20:55 ` Pankaj Gupta
2020-09-29 9:18 ` Wei Yang
2020-09-29 10:12 ` David Hildenbrand
2020-09-30 7:48 ` Wei Yang
2020-10-02 13:24 ` Michal Hocko
2020-10-02 15:20 ` David Hildenbrand
2020-10-05 6:56 ` Michal Hocko
2020-10-05 8:20 ` Mel Gorman [this message]
2020-10-05 9:11 ` David Hildenbrand
2020-09-28 18:21 ` [PATCH v1 4/5] mm/page_alloc: place pages to tail in __free_pages_core() David Hildenbrand
2020-09-28 20:33 ` Pankaj Gupta
2020-09-29 9:36 ` Wei Yang
2020-09-29 10:14 ` David Hildenbrand
2020-10-02 13:41 ` Michal Hocko
2020-10-02 15:10 ` David Hildenbrand
2020-09-28 18:21 ` [PATCH v1 5/5] mm/memory_hotplug: update comment regarding zone shuffling David Hildenbrand
2020-09-29 9:40 ` Wei Yang
2020-10-02 13:41 ` Michal Hocko
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