Re: [PATCH v3 RFC 14/14] mm: speedup page alloc for MPOL_PREFERRED_MANY by adding a NO_SLOWPATH gfp bit

[Feng Tang <feng.tang@intel.com>]

On Wed, Mar 10, 2021 at 10:44:11AM +0100, Michal Hocko wrote:
> On Wed 10-03-21 13:19:47, Feng Tang wrote:
> [...]
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index d66c1c0..00b19f7 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -2205,9 +2205,13 @@ static struct page *alloc_pages_policy(struct mempolicy *pol, gfp_t gfp,
> >  	 * | MPOL_PREFERRED_MANY (round 2) | local         | NULL       |
> >  	 * +-------------------------------+---------------+------------+
> >  	 */
> > -	if (pol->mode == MPOL_PREFERRED_MANY)
> > +	if (pol->mode == MPOL_PREFERRED_MANY) {
> >  		gfp_mask |= __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
> >  
> > +		/* Skip direct reclaim, as there will be a second try */
> > +		gfp_mask &= ~__GFP_DIRECT_RECLAIM;
> 
> __GFP_RETRY_MAYFAIL is a reclaim modifier which doesn't make any sense
> without __GFP_DIRECT_RECLAIM. Also I think it would be better to have a
> proper allocation flags in the initial patch which implements the
> fallback.

Ok, will remove the __GFP_RETRY_MAYFAIL setting and folder this with
previous patch(8/14).

Thanks,
Feng

> > +	}
> > +
> >  	page = __alloc_pages_nodemask(gfp_mask, order,
> >  				      policy_node(gfp, pol, preferred_nid),
> >  				      policy_nodemask(gfp, pol));
> > -- 
> > 2.7.4
> > 
> > 
> 
> -- 
> Michal Hocko
> SUSE Labs