Re: [PATCH] gfp: GFP_RECLAIM_MASK should include __GFP_NO_KSWAPD

Pan Xinhui
2015-10-14T08:20:34Z

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@intel.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@intel.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
>