linux-kernel - Re: [PATCH] gfp: GFP_RECLAIM_MASK should include __GFP_NO

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Date:	Wed, 14 Oct 2015 16:17:31 +0800
From:	Pan Xinhui <xinhuix.pan@...el.com>
To:	Michal Hocko <mhocko@...nel.org>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>, vbabka@...e.cz,
	rientjes@...gle.com, hannes@...xchg.org, nasa4836@...il.com,
	mgorman@...e.de, alexander.h.duyck@...hat.com,
	aneesh.kumar@...ux.vnet.ibm.com,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH] gfp: GFP_RECLAIM_MASK should include __GFP_NO_KSWAPD

hi, Michal
	thanks for your reply :)

On 2015年10月14日 15:34, Michal Hocko wrote:
> On Wed 14-10-15 13:36:51, Pan Xinhui wrote:
>> From: Pan Xinhui <xinhuix.pan@...el.com>
>>
>> GFP_RECLAIM_MASK was introduced in commit 6cb062296f73 ("Categorize GFP
>> flags"). In slub subsystem, this macro controls slub's allocation
>> behavior. In particular, some flags which are not in GFP_RECLAIM_MASK
>> will be cleared. So when slub pass this new gfp_flag into page
>> allocator, we might lost some very important flags.
>>
>> There are some mistakes when we introduce __GFP_NO_KSWAPD. This flag is
>> used to avoid any scheduler-related codes recursive.  But it seems like
>> patch author forgot to add it into GFP_RECLAIM_MASK. So lets add it now.
> 
> This is no longer needed because GFP_RECLAIM_MASK contains __GFP_RECLAIM
> now - have  a look at
> http://lkml.kernel.org/r/1442832762-7247-7-git-send-email-mgorman%40techsingularity.net
> which is sitting in the mmotm tree.
> 

I have a look at Mel's patchset. yes, it can help fix my kswapd issue. :)
So I just need change my kmalloc's gfp_flag to GFP_ATOMIC &~ __GFP_KSWAPD_RECLAIM, then slub will not wakeup kswpad.

thanks
xinhui
 
>> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
>> ---
>>  include/linux/gfp.h | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>> index f92cbd2..9ebad4d 100644
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -130,7 +130,8 @@ struct vm_area_struct;
>>  /* Control page allocator reclaim behavior */
>>  #define GFP_RECLAIM_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS|\
>>  			__GFP_NOWARN|__GFP_REPEAT|__GFP_NOFAIL|\
>> -			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC)
>> +			__GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\
>> +			__GFP_NO_KSWAPD)
>>  
>>  /* Control slab gfp mask during early boot */
>>  #define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_WAIT|__GFP_IO|__GFP_FS))
>> -- 
>> 1.9.1
> 
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