linux-kernel - Re: [RFC PATCH v3 2/3] mm/page_alloc: factor out fallback freepage checking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 2 Feb 2015 22:29:08 +0900
From:	Joonsoo Kim <js1304@...il.com>
To:	Zhang Yanfei <zhangyanfei.ok@...mail.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [RFC PATCH v3 2/3] mm/page_alloc: factor out fallback freepage checking

2015-02-02 21:56 GMT+09:00 Zhang Yanfei <zhangyanfei.ok@...mail.com>:
> Hello Joonsoo,
>
> At 2015/2/2 15:15, Joonsoo Kim wrote:
>> This is preparation step to use page allocator's anti fragmentation logic
>> in compaction. This patch just separates fallback freepage checking part
>> from fallback freepage management part. Therefore, there is no functional
>> change.
>>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>> ---
>>  mm/page_alloc.c | 128 +++++++++++++++++++++++++++++++++-----------------------
>>  1 file changed, 76 insertions(+), 52 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e64b260..6cb18f8 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1142,14 +1142,26 @@ static void change_pageblock_range(struct page *pageblock_page,
>>   * as fragmentation caused by those allocations polluting movable pageblocks
>>   * is worse than movable allocations stealing from unmovable and reclaimable
>>   * pageblocks.
>> - *
>> - * If we claim more than half of the pageblock, change pageblock's migratetype
>> - * as well.
>>   */
>> -static void try_to_steal_freepages(struct zone *zone, struct page *page,
>> -                               int start_type, int fallback_type)
>> +static bool can_steal_fallback(unsigned int order, int start_mt)
>> +{
>> +     if (order >= pageblock_order)
>> +             return true;
>
> Is this test necessary? Since an order which is >= pageblock_order
> will always pass the order >= pageblock_order / 2 test below.
>

Yes, that's true. But, I'd like to remain code as is, because
condition "order >= pageblock_order / 2" is really heuristic and could
be changed someday. Instead of removing it, I will add some comment on it.

Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/