Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature

[Pintu Kumar]

Sorry, looks like some problem with the yahoo mail. Some emails are bouncing.
Sending again with the gmail.


----- Original Message -----
> From: "Valdis.Kletnieks@xxxxxx" <Valdis.Kletnieks@xxxxxx>
> To: Pintu Kumar <pintu.k@xxxxxxxxxxx>
> Cc: corbet@xxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; vbabka@xxxxxxx; gorcunov@xxxxxxxxxx; mhocko@xxxxxxx; emunson@xxxxxxxxxx; kirill.shutemov@xxxxxxxxxxxxxxx; standby24x7@xxxxxxxxx; hannes@xxxxxxxxxxx; vdavydov@xxxxxxxxxxxxx; hughd@xxxxxxxxxx; minchan@xxxxxxxxxx; tj@xxxxxxxxxx; rientjes@xxxxxxxxxx; xypron.glpk@xxxxxx; dzickus@xxxxxxxxxx; prarit@xxxxxxxxxx; ebiederm@xxxxxxxxxxxx; rostedt@xxxxxxxxxxx; uobergfe@xxxxxxxxxx; paulmck@xxxxxxxxxxxxxxxxxx; iamjoonsoo.kim@xxxxxxx; ddstreet@xxxxxxxx; sasha.levin@xxxxxxxxxx; koct9i@xxxxxxxxx; mgorman@xxxxxxx; cj@xxxxxxxxx; opensource.ganesh@xxxxxxxxx; vinmenon@xxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; linux-pm@xxxxxxxxxxxxxxx; cpgs@xxxxxxxxxxx; pintu_agarwal@xxxxxxxxx; vishnu.ps@xxxxxxxxxxx; rohit.kr@xxxxxxxxxxx; iqbal.ams@xxxxxxxxxxx
> Sent: Sunday, 5 July 2015 1:38 AM
> Subject: Re: [PATCH 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature
>
> On Fri, 03 Jul 2015 18:50:07 +0530, Pintu Kumar said:
>
>> This patch provides 2 things:
>
>> 2. Enable shrink_all_memory API in kernel with new CONFIG_SHRINK_MEMORY.
>> Currently, shrink_all_memory function is used only during hibernation.
>> With the new config we can make use of this API for non-hibernation case
>> also without disturbing the hibernation case.
>
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>
>> @@ -3571,12 +3571,17 @@ unsigned long shrink_all_memory(unsigned long
> nr_to_reclaim)
>>       struct reclaim_state reclaim_state;
>>       struct scan_control sc = {
>>           .nr_to_reclaim = nr_to_reclaim,
>> +#ifdef CONFIG_SHRINK_MEMORY
>> +        .gfp_mask = (GFP_HIGHUSER_MOVABLE | GFP_RECLAIM_MASK),
>> +        .hibernation_mode = 0,
>> +#else
>>           .gfp_mask = GFP_HIGHUSER_MOVABLE,
>> +        .hibernation_mode = 1,
>> +#endif
>
>
> That looks like a bug just waiting to happen.  What happens if we
> call an actual hibernation mode in a SHRINK_MEMORY=y kernel, and it finds
> an extra gfp mask bit set, and hibernation_mode set to an unexpected value?
>
Ok, got it. Thanks for pointing this out.
I will handle HIBERNATION & SHRINK_MEMORY case and send again.
I will try to handle it using ifdefs. Do you have any special
suggestions on how this can be handled?
I verified only for the ARM case without hibernation. But, it is
likely that this feature can be enabled in laptop mode also. So we
should handle it.
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