Re: [mm PATCH v5 6/7] mm: Add reserved flag setting to set_page_links

[Pavel Tatashin]

On 18-11-05 13:19:56, Alexander Duyck wrote:
> This patch modifies the set_page_links function to include the setting of
> the reserved flag via a simple AND and OR operation. The motivation for
> this is the fact that the existing __set_bit call still seems to have
> effects on performance as replacing the call with the AND and OR can reduce
> initialization time.
> 
> Looking over the assembly code before and after the change the main
> difference between the two is that the reserved bit is stored in a value
> that is generated outside of the main initialization loop and is then
> written with the other flags field values in one write to the page->flags
> value. Previously the generated value was written and then then a btsq
> instruction was issued.
> 
> On my x86_64 test system with 3TB of persistent memory per node I saw the
> persistent memory initialization time on average drop from 23.49s to
> 19.12s per node.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>

Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>