From: Vlastimil Babka <vbabka@suse.cz>
To: Michal Hocko <mhocko@suse.com>, Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Muchun Song <songmuchun@bytedance.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes
Date: Thu, 18 Mar 2021 10:50:38 +0100 [thread overview]
Message-ID: <843f68e7-6fe6-54e7-976b-af8647482ac1@suse.cz> (raw)
In-Reply-To: <YFIZVvQllaZHDgzW@dhcp22.suse.cz>
On 3/17/21 3:59 PM, Michal Hocko wrote:
> On Wed 17-03-21 15:38:35, Oscar Salvador wrote:
>> On Wed, Mar 17, 2021 at 03:12:29PM +0100, Michal Hocko wrote:
>> > > Since isolate_migratepages_block will stop returning the next pfn to be
>> > > scanned, we reuse the cc->migrate_pfn field to keep track of that.
>> >
>> > This looks hakish and I cannot really tell that users of cc->migrate_pfn
>> > work as intended.
We did check those in detail. Of course it's possible to overlook something...
The alloc_contig_range user never cared about cc->migrate_pfn. compaction
(isolate_migratepages() -> isolate_migratepages_block()) did, and
isolate_migratepages_block() returned the pfn only to be assigned to
cc->migrate_pfn in isolate_migratepages(). I think it's now better that
isolate_migratepages_block() sets it.
>> When discussing this with Vlastimil, I came up with the idea of adding a new
>> field in compact_control struct, e.g: next_pfn_scan to keep track of the next
>> pfn to be scanned.
>>
>> But Vlastimil made me realize that since cc->migrate_pfn points to that aleady,
>> so we do not need any extra field.
Yes, the first patch had at asome point:
/* Record where migration scanner will be restarted. */
cc->migrate_pfn = cc->the_new_field;
Which was a clear sign that the new field is unnecessary.
> This deserves a big fat comment.
Comment where, saying what? :)
next prev parent reply other threads:[~2021-03-18 9:50 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 11:12 [PATCH v5 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-03-17 11:12 ` [PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range Oscar Salvador
2021-03-17 14:05 ` Michal Hocko
2021-03-17 14:42 ` David Hildenbrand
2021-03-17 14:49 ` Michal Hocko
2021-03-18 11:04 ` Oscar Salvador
2021-03-18 11:37 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Oscar Salvador
2021-03-17 14:12 ` Michal Hocko
2021-03-17 14:38 ` Oscar Salvador
2021-03-17 14:59 ` Michal Hocko
2021-03-18 9:50 ` Vlastimil Babka [this message]
2021-03-18 10:22 ` Michal Hocko
2021-03-18 11:10 ` Vlastimil Babka
2021-03-18 11:36 ` Michal Hocko
2021-03-19 9:57 ` Oscar Salvador
2021-03-19 10:14 ` Vlastimil Babka
2021-03-19 10:26 ` Oscar Salvador
2021-03-17 11:12 ` [PATCH v5 3/5] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-03-17 14:22 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 4/5] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-03-17 14:26 ` Michal Hocko
2021-03-18 8:54 ` Oscar Salvador
2021-03-18 9:29 ` Michal Hocko
2021-03-18 9:59 ` Oscar Salvador
2021-03-18 10:12 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig Oscar Salvador
2021-03-17 11:15 ` David Hildenbrand
2021-03-17 14:31 ` Michal Hocko
2021-03-17 14:36 ` David Hildenbrand
2021-03-17 15:03 ` Michal Hocko
2021-03-18 8:44 ` Oscar Salvador
2021-03-18 8:55 ` Michal Hocko
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