From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
David Rientjes <rientjes@google.com>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v3 09/17] mm, compaction: make whole_zone flag ignore cached scanner positions
Date: Tue, 19 Jul 2016 15:44:06 +0900 [thread overview]
Message-ID: <20160719064406.GB17479@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <1c0e2da2-115e-d676-cfec-e572270789ca@suse.cz>
On Mon, Jul 18, 2016 at 11:12:51AM +0200, Vlastimil Babka wrote:
> On 07/06/2016 07:09 AM, Joonsoo Kim wrote:
> >On Fri, Jun 24, 2016 at 11:54:29AM +0200, Vlastimil Babka wrote:
> >>A recent patch has added whole_zone flag that compaction sets when scanning
> >>starts from the zone boundary, in order to report that zone has been fully
> >>scanned in one attempt. For allocations that want to try really hard or cannot
> >>fail, we will want to introduce a mode where scanning whole zone is guaranteed
> >>regardless of the cached positions.
> >>
> >>This patch reuses the whole_zone flag in a way that if it's already passed true
> >>to compaction, the cached scanner positions are ignored. Employing this flag
> >
> >Okay. But, please don't reset cached scanner position even if whole_zone
> >flag is set. Just set cc->migrate_pfn and free_pfn, appropriately. With
>
> Won't that result in confusion on cached position updates during
> compaction where it checks the previous cached position? I wonder
> what kinds of corner cases it can bring...
whole_zone would come along with ignore_skip_hint so I think that
there is no problem on cached position updating.
>
> >your following patches, whole_zone could be set without any compaction
> >try
>
> I don't understand what you mean here? Even after whole series,
> whole_zone is only checked, and positions thus reset, after passing
> the compaction_suitable() call from compact_zone(). So at that point
> we can say that compaction is being actually tried and it's not a
> drive-by reset?
My point is that we should not initialize zone's cached pfn in case of
the whole_zone because what compaction with COMPACT_PRIO_SYNC_FULL
want is just to scan whole range. zone's cached pfn exists for
efficiency and there is no reason to initialize it by compaction with
COMPACT_PRIO_SYNC_FULL. If there are some parallel compaction users,
they could be benefit from un-initialized zone's cached pfn so I'd
like to leave them.
Thanks.
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next prev parent reply other threads:[~2016-07-19 6:39 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-24 9:54 [PATCH v3 00/17] make direct compaction more deterministic Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 01/17] mm, compaction: don't isolate PageWriteback pages in MIGRATE_SYNC_LIGHT mode Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 02/17] mm, page_alloc: set alloc_flags only once in slowpath Vlastimil Babka
2016-06-30 14:44 ` Michal Hocko
2016-06-24 9:54 ` [PATCH v3 03/17] mm, page_alloc: don't retry initial attempt " Vlastimil Babka
2016-06-30 15:03 ` Michal Hocko
2016-06-24 9:54 ` [PATCH v3 04/17] mm, page_alloc: restructure direct compaction handling " Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 05/17] mm, page_alloc: make THP-specific decisions more generic Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 06/17] mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 07/17] mm, compaction: introduce direct compaction priority Vlastimil Babka
2016-06-24 11:39 ` kbuild test robot
2016-06-24 11:51 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 08/17] mm, compaction: simplify contended compaction handling Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 09/17] mm, compaction: make whole_zone flag ignore cached scanner positions Vlastimil Babka
2016-07-06 5:09 ` Joonsoo Kim
2016-07-18 9:12 ` Vlastimil Babka
2016-07-19 6:44 ` Joonsoo Kim [this message]
2016-07-19 6:54 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 10/17] mm, compaction: cleanup unused functions Vlastimil Babka
2016-06-24 11:53 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 11/17] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 12/17] mm, compaction: more reliably increase " Vlastimil Babka
2016-07-06 5:39 ` Joonsoo Kim
2016-07-15 13:37 ` Vlastimil Babka
2016-07-18 4:41 ` Joonsoo Kim
2016-07-18 12:21 ` Vlastimil Babka
2016-07-19 4:53 ` Joonsoo Kim
2016-07-19 7:42 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 13/17] mm, compaction: use correct watermark when checking allocation success Vlastimil Babka
2016-07-06 5:47 ` Joonsoo Kim
2016-07-18 9:23 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 14/17] mm, compaction: create compact_gap wrapper Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 15/17] mm, compaction: use proper alloc_flags in __compaction_suitable() Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 16/17] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 17/17] mm, vmscan: make compaction_ready() more accurate and readable Vlastimil Babka
2016-07-06 5:55 ` Joonsoo Kim
2016-07-18 11:48 ` Vlastimil Babka
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