On 2015/6/29 15:32, Kamezawa Hiroyuki wrote:
> On 2015/06/27 11:24, Xishi Qiu wrote:
>> This patch introduces a new migratetype called "MIGRATE_MIRROR", it is used to
>> allocate mirrored pages.
>> When cat /proc/pagetypeinfo, you can see the count of free mirrored blocks.
>>
>> Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
>
> My fear about this approarch is that this may break something existing.
>
> Now, when we add MIGRATE_MIRROR type, we'll hide attributes of pageblocks as
> MIGRATE_UNMOVABOLE, MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE.
>
> Logically, MIRROR attribute is independent from page mobility and this overwrites
> will make some information lost.
>
> Then,
>
>> ---
>> include/linux/mmzone.h | 9 +++++++++
>> mm/page_alloc.c | 3 +++
>> mm/vmstat.c | 3 +++
>> 3 files changed, 15 insertions(+)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index 54d74f6..54e891a 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -39,6 +39,9 @@ enum {
>> MIGRATE_UNMOVABLE,
>> MIGRATE_RECLAIMABLE,
>> MIGRATE_MOVABLE,
>> +#ifdef CONFIG_MEMORY_MIRROR
>> + MIGRATE_MIRROR,
>> +#endif
>
> I think
> MIGRATE_MIRROR_UNMOVABLE,
> MIGRATE_MIRROR_RECLAIMABLE,
> MIGRATE_MIRROR_MOVABLE, <== adding this may need discuss.
> MIGRATE_MIRROR_RESERVED, <== reserved pages should be maintained per mirrored/unmirrored.
>
Hi Kame,
You mean add 3 or 4 new migratetype?
> should be added with the following fallback list.
>
> /*
> * MIRROR page range is defined by firmware at boot. The range is limited
> * and is used only for kernel memory mirroring.
> */
> [MIGRATE_UNMOVABLE_MIRROR] = {MIGRATE_RECLAIMABLE_MIRROR, MIGRATE_RESERVE}
> [MIGRATE_RECLAIMABLE_MIRROR] = {MIGRATE_UNMOVABLE_MIRROR, MIGRATE_RESERVE}
>
Why not like this:
{MIGRATE_RECLAIMABLE_MIRROR, MIGRATE_MIRROR_RESERVED, MIGRATE_RESERVE}
> Then, we'll not lose the original information of "Reclaiable Pages".
>
> One problem here is whteher we should have MIGRATE_RESERVE_MIRROR.
>
> If we never allow users to allocate mirrored memory, we should have MIGRATE_RESERVE_MIRROR.
> But it seems to require much more code change to do that.
>
> Creating a zone or adding an attribues to zones are another design choice.
>
If we add a new zone, mirror_zone will span others, I'm worry about this
maybe have problems.
Thanks,
Xishi Qiu
> Anyway, your patch doesn't takes care of reserved memory calculation at this point.
> Please check setup_zone_migrate_reserve() That will be a problem.
>
> Thanks,
> -Kame
>
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