Re: [PATCH 2/4] mm: Create non-atomic version of SetPageReserved for init use

[Pasha Tatashin]

On 9/10/18 7:43 PM, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
> 
> It doesn't make much sense to use the atomic SetPageReserved at init time
> when we are using memset to clear the memory and manipulating the page
> flags via simple "&=" and "|=" operations in __init_single_page.
> 
> This patch adds a non-atomic version __SetPageReserved that can be used
> during page init and shows about a 10% improvement in initialization times
> on the systems I have available for testing. On those systems I saw
> initialization times drop from around 35 seconds to around 32 seconds to
> initialize a 3TB block of persistent memory.
> 
> I tried adding a bit of documentation based on commit <f1dd2cd13c4> ("mm,
> memory_hotplug: do not associate hotadded memory to zones until online").
> 
> Ideally the reserved flag should be set earlier since there is a brief
> window where the page is initialization via __init_single_page and we have
> not set the PG_Reserved flag. I'm leaving that for a future patch set as
> that will require a more significant refactor.
> 
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>

Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>

Thank you,
Pavel