From: Wei Yang <richardw.yang@linux.intel.com>
To: David Hildenbrand <david@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>,
akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, mhocko@suse.com,
yang.shi@linux.alibaba.com, rientjes@google.com
Subject: Re: [Patch v2 4/4] mm/migrate.c: handle same node and add failure in the same way
Date: Thu, 30 Jan 2020 06:07:23 +0800 [thread overview]
Message-ID: <20200129220723.GC20736@richard> (raw)
In-Reply-To: <17796dbb-b9b6-9481-5048-addfa5eec51e@redhat.com>
On Wed, Jan 29, 2020 at 11:13:23AM +0100, David Hildenbrand wrote:
>On 22.01.20 02:16, Wei Yang wrote:
>> When page is not queued for migration, there are two possible cases:
>>
>> * page already on the target node
>> * failed to add to migration queue
>>
>> Current code handle them differently, this leads to a behavior
>> inconsistency.
>>
>> Usually for each page's status, we just do store for once. While for the
>> page already on the target node, we might store the node information for
>> twice:
>>
>> * once when we found the page is on the target node
>> * second when moving the pages to target node successfully after above
>> action
>>
>> The reason is even we don't add the page to pagelist, but store_status()
>> does store in a range which still contains the page.
>>
>> This patch handles these two cases in the same way to reduce this
>> inconsistency and also make the code a little easier to read.
>>
>
>I'd rephrase to
>
>"mm/migrate.c: unify "not queued for migration" handling in do_pages_move()
>
>It can currently happen that we store the status of a page twice:
>* Once we detect that it is already on the target node
>* Once we moved a bunch of pages, and a page that's already on the
> target node is contained in the current interval.
>
>Let's simplify the code and always call do_move_pages_to_node() in
>case we did not queue a page for migration. Note that pages that are
>already on the target node are not added to the pagelist and are,
>therefore, ignored by do_move_pages_to_node() - there is no functional
>change.
>
>The status of such a page is now only stored once.
>"
>
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> ---
>> mm/migrate.c | 16 ++++++++--------
>> 1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 80d2bba57265..591f2e5caed6 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1654,18 +1654,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>> err = add_page_for_migration(mm, addr, current_node,
>> &pagelist, flags & MPOL_MF_MOVE_ALL);
>>
>> - if (!err) {
>> - /* The page is already on the target node */
>> - err = store_status(status, i, current_node, 1);
>> - if (err)
>> - goto out_flush;
>> - continue;
>> - } else if (err > 0) {
>> + if (err > 0) {
>> /* The page is successfully queued for migration */
>> continue;
>> }
>>
>> - err = store_status(status, i, err, 1);
>> + /*
>> + * Two possible cases for err here:
>> + * == 0: page is already on the target node, then store
>> + * current_node to status
>> + * < 0: failed to add page to list, then store err to status
>> + */
>
>I'd shorten that to
>
>/*
> * If the page is already on the target node (!err), store the node,
> * otherwise, store the err.
>*/
>
>> + err = store_status(status, i, err ? : current_node, 1);
>> if (err)
>> goto out_flush;
>>
>>
>
>Thanks!
>
>Reviewed-by: David Hildenbrand <david@redhat.com>
>
Yep, thanks.
I would take this :-)
>--
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
prev parent reply other threads:[~2020-01-29 22:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 1:16 [Patch v2 0/4] cleanup on do_pages_move() Wei Yang
2020-01-22 1:16 ` [Patch v2 1/4] mm/migrate.c: not necessary to check start and i Wei Yang
2020-01-28 10:04 ` David Hildenbrand
2020-01-29 0:32 ` Wei Yang
2020-01-22 1:16 ` [Patch v2 2/4] mm/migrate.c: wrap do_move_pages_to_node() and store_status() Wei Yang
2020-01-28 10:14 ` David Hildenbrand
2020-01-29 0:38 ` Wei Yang
2020-01-29 9:28 ` David Hildenbrand
2020-01-29 22:00 ` Wei Yang
2020-01-22 1:16 ` [Patch v2 3/4] mm/migrate.c: check pagelist in move_pages_and_store_status() Wei Yang
2020-01-28 10:21 ` David Hildenbrand
2020-01-29 0:46 ` Wei Yang
2020-01-29 9:36 ` David Hildenbrand
2020-01-22 1:16 ` [Patch v2 4/4] mm/migrate.c: handle same node and add failure in the same way Wei Yang
2020-01-29 10:13 ` David Hildenbrand
2020-01-29 22:07 ` Wei Yang [this message]
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